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This article reports on the second Young Environmental Scientists Meeting that was hosted from 28 February to 2 March 2011 by the Institute for Environmental Research at RWTH Aachen University, Germany. This extraordinary meeting was again initiated and organized by the Student Advisory Council under the umbrella of Society of Environmental Toxicology and Chemistry Europe. A movie about the meeting and the abstracts of poster and platform presentations are freely available as supplemental material of this article.
Endocrine disrupting compounds (EDCs) emerged as a major concern for water quality in the last decade and have been studied extensively since. Besides typical natural and synthetic estrogens also petroleum product compounds such as some PAHs have been identified as potential EDCs, revealing endocrine disruption to be a relevant mode of action for crude oil toxicity. Hence, in the context of a comprehensive retro- or prospective risk assessment of oil spills the implementation of mechanism-specific toxicity such as endocrine disruption is of high importance. To evaluate the exposure risk for the aquatic biota, research focuses on water-soluble fractions underlying an oil slick that could be simulated via water-accommodated fractions (WAF). Against this background human (ERα-CALUX®) and yeast based (A-YES®) reporter gene bioassays were successfully optimized for the application in estrogenicity evaluation of the water-accommodated fraction (WAF) from a crude oil. Combining different approaches, the estrogenicity of the WAFs from a naphthenic North Sea crude oil was tested with and without the addition of a chemical dispersant addressing specific aspects of estrogenicity including the influence of biotransformation capacities and different salinity conditions. Both the WAF free from droplets (LEWAF) as well as the chemically dispersed WAF (CEWAF) gave indications of an ER-mediated estrogenicity with much stronger ERα agonists in the CEWAF treatment. Resulting estradiol equivalents of the WAFs were above the established effect-based trigger values for both bioassays. Results indicate that the dispersant rather increased the fraction of ER-activating crude oil compounds instead of interacting with the receptor itself. Only slight changes in estrogenic responses were observed when cells capable of active metabolism (T47D) were used instead of cells without endogenous metabolism (U2-OS) in the recombinant ER transactivation CALUX assay. With the yeast cells a higher estrogenic activity was observed in the experiments under elevated salinity conditions (6‰), which was in contrast to previous expectations due to typical decrease in dissolved PAH fraction with increasing salinity (salting-out effect) but might be related to increased cell sensitivity.
Background: The environmental impact of pesticides has been an increasingly discussed issue over the last decades. Constant usage of pesticides presents a burden for soil and causes a decrease in its health, including the negative effects on earthworms which are indicators for soil quality. The objective of this research was the assessment of the effects of two insecticides and two herbicides on the earthworm Eisenia andrei. Namely, the following active ingredients and respective commercial preparations were investigated: esfenvalerate (Sumialfa), thiacloprid (Calypso), dimethenamid-p (Frontier) and prosulfocarb (Filon). Lethal concentrations (48 h) of both active ingredient and commercial preparations were determined using the filter paper contact test. Results: The results showed that Calypso and Frontier were significantly more toxic than the active ingredient. Therefore, all further measurements were performed after exposure of earthworms to the commercial preparations of the pesticides. Specifically, several enzymatic biomarkers and multixenobiotic resistance activity were assessed. Additionally, a fluorescence-based assay for the determination of oxidative stress was established. Significant changes were detected for catalase, carboxylesterase and multixenobiotic activities after 48-h exposures. Also, a significant change in oxidative stress parameters could be observed for both Calypso and Frontier. Conclusions: The obtained results show that commercial preparations can be more toxic than the active ingredients, and the formulations being distributed in the environment can affect earthworms on a molecular level already after short exposures. This emphasizes the importance of a more integrated eco-toxicological assessment of commercial pesticide preparations not to underestimate their effects on the environment.
Background: The application of chemical dispersants is a common remediation strategy when accidental oil spills occur in aquatic environments. Breaking down the oil slick into small droplets, dispersants facilitate the increase of particulate and dissolved oil compounds, enhancing the bioavailability of toxic oil constituents. The aim of the present work was to explore the effects of water accommodated fractions (WAF) of a naphthenic North Sea crude oil produced with and without the addition of the chemical dispersant FINASOL OSR 52 to adult zebrafish exposed for 3 and 21 d. Fish were exposed to environmentally relevant concentrations of 5% and 25% WAFOIL (1:200) and to 5% WAFOIL+D (dispersant–oil ratio 1:10) in a semi-static exposure setup. Results: The chemically dispersed WAF presented a 20-fold increase of target polycyclic aromatic hydrocarbons (PAHs) in the water phase compared to the corresponding treatment without dispersant and was the only treatment resulting in markedly bioaccumulation of PAHs in carcass after 21 d compared to the control. Furthermore, only 5% WAFOIL+D caused fish mortality. In general, the undispersed oil treatments did not lead to significant effects compared to control, while the dispersed oil induced significant alterations at gene transcription and enzyme activity levels. Significant up-regulation of biotransformation and oxidative stress response genes (cyp1a, gstp1, sod1 and gpx1a) was recorded in the livers. For the same group, a significant increment in EROD activity was detected in liver along with significant increased GST and CAT activities in gills. The addition of the chemical dispersant also reduced brain AChE activity and showed a potential genotoxic effect as indicated by the increased frequency of micronuclei in erythrocytes after 21 d of exposure. Conclusions: The results demonstrate that the addition of chemical dispersants accentuates the effect of toxic compounds present in oil as it increases PAH bioavailability resulting in diverse alterations on different levels of biological organization in zebrafish. Furthermore, the study emphasizes the importance to combine multilevel endpoints for a reliable risk assessment due to high variable biomarker responses. The present results of dispersant impact on oil toxicity can support decision making for oil spill response strategies.
Petroleum products including crude oils and refined distillates are unique environmental pollutants consisting of thousands of compounds with varying physical-chemical properties and resulting toxicity for aquatic biota. Hence, for a reliable risk assessment individual petroleum product toxicity profiles are needed. Furthermore, the influence of oil spill response strategies like the application of chemical dispersants has to be implemented. The present study addressed the toxicity of water-accommodated fractions (WAFs) of two different oil types on fish early life stages on different biological organization levels in the laboratory model species Danio rerio. Experiments with a 3rd generation dispersant used in loading rated resembling the exposure in experiments with chemically dispersed oils were included, enabling a direct comparability of results. This approach is of high importance as especially the investigation of dispersant toxicity in relevant exposure concentrations is rather scarce. Zebrafish embryos were exposed to different WAFs shortly after and up to 120 hour post fertilization (hpf). Besides phenotypic effects including edema and spine deformations, reduced responses to dark stimuli, increased CYP1A activity and marginal AChE inhibition were observed in sublethal effect concentrations. Both oil types had varying strength of toxicity, which did not correlate with corresponding chemical analysis of target PAHs. Chemically dispersed oils induced stronger acute toxicity in zebrafish embryos compared to native (initial) oil exposure, which was further reflected by very low exposure concentrations for biomarker endpoints. Based on a comparison to the dispersant alone, a higher toxicity of dispersed oils was related to a combination of dispersant toxicity and an elevated crude oil compound bioavailability, due to dispersion-related partitioning kinetics. In contrast to LEWAF and CEWAF neither typical morphological effects nor mechanism-specific toxicity were observed for the dispersant alone, indicating narcosis as the responsible cause of effects.
In situ burning (ISB) is discussed to be one of the most suitable response strategies to combat oil spills in extreme conditions. After burning, a highly viscous and sticky residue is left and may over time pose a risk of exposing aquatic biota to toxic oil compounds. Scientific information about the impact of burn residues on the environment is scarce. In this context, a comprehensive ISB field experiment with approx. 1000L IFO 180 was conducted in a fjord in Greenland. The present study investigated the toxicity of collected ISB residues to early life stages of zebrafish (Danio rerio) as a model for potentially exposed pelagic organisms. The toxicity of ISB residues on zebrafish embryos was compared with the toxicity of the initial (unweathered) IFO 180 and chemically dispersed IFO 180. Morphological malformations, hatching success, swimming behavior, and biomarkers for exposure (CYP1A activity, AChE inhibition) were evaluated in order to cover the toxic response on different biological organization levels. Across all endpoints, ISB residues did not induce greater toxicity in zebrafish embryos compared with the initial oil. The application of a chemical dispersant increased the acute toxicity most likely due to a higher bioavailability of dissolved and particulate oil components. The results provide insight into the adverse effects of ISB residues on sensitive life stages of fish in comparison with chemical dispersant application.
Genotoxicity assessment is of high relevance for crude and refined petroleum products, since oil compounds are known to cause DNA damage with severe consequences for aquatic biota as demonstrated in long-term monitoring studies. This study aimed at the optimization and evaluation of small-scale higher-throughput assays (Ames fluctuation, micronucleus, Nrf2-CALUX®) covering different mechanistic endpoints as first screening tools for genotoxicity assessment of oils. Cells were exposed to native and chemically dispersed water-accommodated fractions (WAFs) of three oil types varying in their processing degree. Independent of an exogenous metabolic activation system, WAF compounds induced neither base exchange nor frame shift mutations in bacterial strains. However, significantly increased chromosomal aberrations in zebrafish liver (ZF-L) cells were observed. Oxidative stress was indicated for some treatments and was not correlated with observed DNA damage. Application of a chemical dispersant increased the genotoxic potential rather by the increased bioavailability of dissolved and particulate oil compounds. Nonetheless, the dispersant induced a clear oxidative stress response, indicating a relevance for general toxic stress. Results showed that the combination of different in vitro assays is important for a reliable genotoxicity assessment. Especially, the ZF-L capable of active metabolism and DNA repair seems to be a promising model for WAF testing.
