The project goal was to support the regulatory acceptance of data generated with the OECD Acute Fish Embryo Toxicity Test (TG 236) as alternative method to the OECD Acute Fish Toxicity Test (TG 203). TG 236 is an important contribution to animal welfare in chemical safety assessment in Europe but also worldwide. Results of the project are directly used within OECD project 2.54 on the Development of a Guidance Document for an Integrated Approach to Testing and Assessment of Acute Fish Toxicity. Specific results: (1) the knowledge on xenobiotic transformation capacities in zebrafish embryos, juveniles and adults is fragmentary. Therefore, transfer of biotransformation data from juvenile fish to adult fish does not appear justified. (2) The chorion is no barrier for uncharged industrial chemicals of a molecular size of 3,000 – 4,000 Da. Veröffentlicht in Texte | 94/2020.
In view of the advanced development of new specific active pharmaceutical ingredients, the question arises as to whether the established standard procedures for the environmental risk assessment in the context of marketing authorization are still sufficient to adequately cover relevant effects on environmental organisms. The focus of this project is on specific test strategies for substances from the group of oncologicals, cardiologicals and statins, as well as their experimental verification in case studies. Studies with aquatic plants in the Lemna sp. Growth Inhibition Test ( OECD 221), the zebrafish embryo toxicity test (OECD 236) amended with sublethal endpoints and the comet assay with environmentally relevant cell types are discussed as possible adaptations, although not all of them proved to be suitable. Veröffentlicht in Texte | 21/2024.
Im Juli 2013 wurde der akute Fischembryotest (FET) als OECD-Richtlinie 236 anerkannt. Der FET stellt damit die erste voll validierte Alternativmethode im Rahmen des OECD-Testrichtlinienprograms im Bereich der Ökotoxikologie dar. Die praktische Anwendbarkeit wurde jedoch seitdem hinsichtlich mehrerer Aspekte diskutiert, die im vorliegenden Bericht adressiert werden: Im Hinblick auf die potentielle Barrierefunktion der Eihülle des Zebrabärblings konnte eine Molekulargröße von 3000 - 4000 Da für die freie Passage ungeladener Moleküle identifiziert werden. Das Limit für die Passage geladener Moleküle ist geringer. DMSO-Konzentrationen >= 0,1 % reduzieren die Barrierefunktion weiter. Embryonen, juvenile und erwachsene Zebrabärblinge sind im Hinblick auf ihre Biotransformation unterschiedlich gut untersucht; insgesamt ist unser Wissen ungenügend. Wann immer die Biotransformation in Embryonen genauer betrachtet wurde, konnte sie zumindest qualitativ nachgewiesen werden. Die Übertragung von Daten zu juvenilen Fischen auf erwachsene und umgekehrt ist genauso unmöglich wie die Übertragung von Daten von Säugetieren auf Fische. Die Analyse eines historischen Datensatzes zur akuten Fischtoxizität, der bereits als Grundlage für die Bewertung der Eignung des FET gedient hatte, ging von 2936 Studien mit Daten zu 1842 Substanzen aus. Die Anwendung der gleichen Filter, die von der ECHA für den FET angesetzt wurden, führte zum Ausschluss von 65,4 % der Studien bzw. 81,8 % der Substanzen. Die Daten des vorliegenden Berichts werden in das OECD-Projekt Nr. 254 ("Guidance Document on an Integrated Approach on Testing and Assessment for Fish Acute Toxicity Testing" - Integration of the Fish Embryo Test into the Threshold Approach") integriert. Quelle: Forschungsbericht
Environmental risk assessments of organic chemicals usually do not consider pH as a key factor. Hence, most substances are tested at a single pH only, which may underestimate the toxicity of ionisable substances with a pKa in the range of 4-10. Thus, the ability to consider the pH-dependent toxicity would be crucial for a more realistic assessment. Moreover, there is a tendency in acute toxicity tests to focus on mortality only, while little attention is paid to sublethal endpoints. We used Danio rerio embryos exposed to ten ionisable substances (the acids diclofenac, ibuprofen, naproxen and triclosan and the bases citalopram, fluoxetine, metoprolol, propranolol, tramadol and tetracaine) at four external pH levels, investigating the endpoints mortality (LC50) and heart rate (EC20). Dose-response curves were fitted with an ensemble-model to determine the true uncertainty and variation around the mean endpoints. The ensemble considers eight (heart rate) or twelve (mortality) individual models for binominal and Poisson distributed data, respectively, selected based on the Akaike Information Criterion (AIC). In case of equally good models, the mean endpoint of all models in the ensemble was calculated, resulting in more robust ECx estimates with lower 'standard errors' as compared to randomly selected individual models. We detected a high correlation between mortality (LC50) at 96 hpf and reduced heart rate (EC20) at 48 hpf for all compounds and all external pH levels (r = 0.98). Moreover, the observed pH-dependent effects were strongly associated with log D and thus, likely driven by differences in uptake (toxicokinetic) rather than internal (toxicodynamic) processes. Prospectively, the a priori consideration of pH-dependent effects of ionisable substances might make testing at different pH levels redundant, while the endpoint of mortality might even be replaced by a reliable sublethal proxy that would reduce the exposure, accelerating the evaluation process. © 2021 The Authors
Low molecular weight phthalates, such as diethyl phthalate (DEP), benzyl butyl phthalate (BBzP), or diisobutyl phthalate (DiBP), are suspected to disrupt endocrine system. However, their adverse effects on sex steroid hormones and underlying mechanisms are not well-documented. The aim of this study is to investigate the effects of major low molecular weight phthalates (LMWPs), i.e., DEP, BBzP, and DiBP, and their hydrolytic metabolites, on sex steroid hormone system, employing male zebrafish and/or a human adrenocortical carcinoma (H295R) cell. In male zebrafish, 14-day exposure to DEP, BBzP, or DiBP significantly decreased testosterone (T) concentrations. All test compounds significantly up-regulated cyp19agene expression, and down-regulated starand 3âhsd genes in the male fish. In H295R cell, all test compounds except monoisobutyl phthalate (MiBP) reduced T concentrations and increased E2/T ratio. Gene expression changes in H295R cell, e.g., significant down-regulation of StARgene and up-regulation of CYP19A gene, supported depressed synthesis of sex hormones in the adrenal cell. Our results show that not only DEP, BBzP, and DiBP, but also their hydrolytic metabolites disrupt sex hormone balances through modulating key steroidogenic genes in the human adrenal cells and in zebrafish.Quelle: http://www.sciencedirect.com/
Developmental toxicity refers to the occurrence of adverse effects on a developing organism as a consequence of exposure to hazardous chemicals. The assessment of developmental toxicity has become relevant to the safety assessment process of chemicals. The zebrafish embryo developmental toxicology assay is an emerging test used to screen the teratogenic potential of chemicals and it is proposed as a promising test to replace teratogenic assays with animals. Supported by the increased availability of data from this test, the developmental toxicity assay with zebrafish has become an interesting endpoint for the in silico modelling. The purpose of this study was to build up quantitative structure-activity relationship (QSAR) models. In this work, new in silico models for the evaluation of developmental toxicity were built using a well-defined set of data from the ToxCastTM Phase I chemical library on the zebrafish embryo. Categorical and continuous QSAR models were built by gradient boosting machine learning and the Monte Carlo technique respectively, in accordance with Organization for Economic Co-operation and Development principles and their statistical quality was satisfactory. The classification model reached balanced accuracy 0.89 and Matthews correlation coefficient 0.77 on the test set. The regression model reached correlation coefficient R2 0.70 in external validation and leave-one-out cross-validated Q2 0.73 in internal validation. © 2020 Elsevier Inc.
In einer Literaturstudie mit dem Ziel, sensitive Organismen und organismische Endpunkte sowie geeignete in vitro-Testsysteme für ein Biomonitoring von Arzneimitteln zu identifizieren, wurde die bestehende Datenbank OEKOTOX um Wirkdaten für 90 Arzneimittel von hoher Priorität bis 2013 erweitert. Niedrigste Effektkonzentrationen wurden identifiziert und die jeweiligen Studien auf Reliabilität überprüft. Reliable MECmax/LOECmin-Werte >0.1 wurden für Diclofenac bei mehr als 3 Organismengruppen und für Propranolol, Sulfamethoxazol, Bezafibrat, 17 ß-Ethinlyestradiol, 17ß-Estradiol und Oxytetrazyclin bei 2 Organismengruppen identifiziert. Als reliabel sensitivste Organismen erwiesen sich Danio rerio, Oncorhynchus mykiss, Oryzias latipes, Elliptio complanata und Potamopyrgus antipodarum. Der sensitivste Wirkendpunkt waren Verhaltensänderungen. Des Weiteren wurden der Wissensstand zu in vitro-Verfahren zum Nachweis von Arzneimittel-Effekten sowie Vor- und Nachteile dieser biochemischen und zellbasierten Assays recherchiert. Auf dieser Basis wird für ein künftiges Biomonitoring von Arzneimitteln empfohlen, Wirkstoffklassenspezifische in vitro-Testsysteme für ß-Blocker und nichtsteroidale Analgetika zu entwickeln und deren Signale mit in vivo-Reaktionen o.g. sensitiver bzw. für deutsche Fließgewässer relevanter Organismen abzugleichen.<BR>Quelle: Forschungsbericht
In einer Literaturstudie mit dem Ziel, sensitive Organismen und organismische Endpunkte sowie geeignete in vitro-Testsysteme für ein Biomonitoring von Arzneimitteln zu identifizieren, wurde die bestehende Datenbank OEKOTOX um Wirkdaten für 90 Arzneimittel von hoher Priorität bis 2013 erweitert. Niedrigste Effektkonzentrationen wurden identifiziert und die jeweiligen Studien auf Reliabilität überprüft. Reliable MECmax/LOECmin-Werte >0.1 wurden für Diclofenac bei mehr als 3 Organismengruppen und für Propranolol, Sulfamethoxazol, Bezafibrat, 17á-Ethinlyestradiol, 17â-Estradiol und Oxytetrazyclin bei 2 Organismengruppen identifiziert. Als reliabel sensitivste Organismen erwiesen sich Danio rerio, Oncorhynchus mykiss, Oryzias latipes, Elliptio complanata und Potamopyrgus antipodarum. Der sensitivste Wirkendpunkt waren Verhaltensänderungen. Des Weiteren wurden der Wissensstand zu in vitro-Verfahren zum Nachweis von Arzneimittel-Effekten sowie Vor- und Nachteile dieser biochemischen und zellbasierten Assays recherchiert. Auf dieser Basis wird für ein künftiges Biomonitoring von Arzneimitteln empfohlen, Wirkstoffklassen-spezifische in vitro-Testsysteme für â-Blocker und nichtsteroidale Analgetika zu entwickeln und deren Signale mit in vivo-Reaktionen o.g. sensitiver bzw. für deutsche Fließgewässer relevanter Organismen abzugleichen.<BR>Quelle: Forschungsbericht
Little is known about the ecotoxicity of heterocyclic aromatic hydrocarbons (NSO-HETs) to aquatic organisms. In the environment, NSO-HETs have been shown to occur in a strong association with their unsubstituted carbocyclic analogues, the polycyclic aromatic hydrocarbons (PAH), for which much more information is available. The present study addressed this issue by investigating the toxicity of four selected NSO-HETs in green algae (Desmodesmus subspicatus), daphnids (Daphnia magna) and fish embryos (Danio rerio). The four high molecular weight NSO-HETs dibenz[a,j]acridine (DBA), 7H-dibenzo[c,g]carbazole (DBC), benzo[b]naphtho[2,1-d]thiophene (BNT) and benzo[b]naphtho[1,2-d]furan (BNF) were selected, based on the results of a previous research project, indicating a lack of toxicity data and a high potential for persistence and bioaccumulation. The solubilities of the NSO-HETs in the test media were determined and turned out to be comparatively low (2.7-317ng/L) increasing in the following order: DBA < BNT " DBC " BNF. Exposure concentrations during the toxicity tests were quantified with GC-MS and decreased strongly possibly due to sorption or metabolising during the test periods (48-96 h). Therefore, the estimated effect concentrations were related to the mean measured concentrations, as endpoints related to nominal concentrations would have underestimated the toxicity many times over. Within the range of the substance solubilities, BNF affected all test organisms with fish embryos being the most sensitive (fish: EC50 6.7 ng/L, algae: EC10 17.8 ng/L, daphnids: EC50 55.8 ng/L). DBC affected daphnids (EC50 2.5 ng/L,) and algae (EC10 3.1 ng/L), but not fish embryos. The lowest toxicity endpoint was observed for BNT affecting only algae (NOEC 0.556 ng/L) and neither daphnids nor fish embryos. DBA did not show any effects on the tested organisms in the range of the water solubility. However, we would expect effects in long-term toxicity studies to fish and aquatic invertebrates for all substances at lower concentrations, which needs further investigation. All four NSO-HETs were identified in mussels (Mytilus edulis) from the German coasts, in green kale (Brassica oleracea var. acephala) and in freshwater harbor sediment in concentrations between 0.07 and 2 ng/kg, highlighting their relevance as environmental contaminants. There is a need to regulate the four NSO-HETs within the REACH regulation due to their intrinsic properties and their environmental relevance. However, acquisition of additional experimental data appears to be pivotal for a regulation under REACH. © 2018 The Authors. Published by Elsevier Inc.
Depending on the ambient pH, ionizable substances are present in varying proportions in their neutral or charged form. The extent to which these two chemical species contribute to the pH-dependant toxicity of ionizable chemicals and whether intracellular ion trapping has a decisive influence in this context is controversially discussed. Against this background, we determined the acute toxicity of 24 ionizable substances at up to 4 different pH values on the embryonic development of the zebrafish, Danio rerio, and supplemented this dataset with additional data from the literature. The LC50 for some substances (diclofenac, propranolol, fluoxetine) differed by a factor of even >103 between pH5 and pH9. To simulate the toxicity of 12 acids and 12 bases, six models to calculate a pH-dependant logD value as a proxy for the uptake of potentially toxic molecules were created based on different premises for the trans-membrane passage and toxic action of neutral and ionic species, and their abilities to explain the real LC50 data set were assessed. Using this approach, we were able to show that both neutral and charged species are almost certainly taken up into cells according to their logD-based distribution, and that both species exert toxicity. Since two of the models that assume all intracellular molecules to be neutral overestimated the real toxicity, it must be concluded, that the toxic effect of a single charged intracellularly present molecule is, on the average, lower than that of a single neutral molecule. Furthermore, it was possible to attribute differences in toxicity at different pH values for these 24 ionizable substances to the respective deltas in logD at these pH levels with high accuracy, enabling particularly a full logD-based model on the basis of logPow as a membrane passage descriptor to be used for predicting potential toxicities in worst-case scenarios from existing experimental studies, as stipulated in the process of registration of chemicals and the definition of Environmental Quality Standards (EQS). © 2023 The Author(s).
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