Previous studies exposing fish to xenoestrogens have demonstrated vitellogenin (VTG) induction, delayed gametogenesis, altered sex distribution, and decreased reproductive performance, with a majority of those studies focusing on exposure to single chemicals. The objective of this study was to determine the effects of binary mixtures of a weak estrogen receptor agonist, nonylphenol (NP) and a potent estrogen receptor agonist, 17α-ethinylestradiol (EE) on sex distribution, gametogenesis, VTG induction, heat shock protein 70 (HSP70) expression and reproductive capacity in zebrafish (Danio rerio). Fish were exposed from 2 to 60 days post-hatch (dph) to nominal concentrations of 10 or 100 µg/l NP (NP10 or NP100, respectively), 1 or 10 ng/l EE (EE1 or EE10, respectively), 1 ng/l EE + 10 or 100 µg/l NP (EE1+NP10 or EE1+NP100, respectively), 10 ng/l EE + 10 or 100 µg/l NP (EE10+NP10 or EE10+NP100, respectively) or solvent control (0.01% acetone v/v) in a static-renewal system with replacement every 48h. At 60 dph, fish from each treatment were euthanized for histological examination of gonads, and whole body VTG and HSP70 levels. Remaining fish were reared in clean water until adulthood (240 dph) for breeding studies. In all EE10 exposure groups (EE10, EE10+NP10 and EE10+NP100), increasing NP concentration acted less than additively to the action of EE in terms of VTG induction at 60 dph. Similarly, a less than additivity of effect was observed with egg production, where EE1+NP100 exposure resulted in significantly more eggs produced per breeding trial than EE1 alone. Histological staging of oogenesis revealed suppressed gametogenesis in females at 60 dph. There were no differences among treatment groups in whole body HSP70 expression in 60 dph fish or in gonadal HSP70 expression in adult fish. Although there was no statistical evidence of non-additivity, breeding trials in adults revealed significant reductions in egg viability, egg hatchability and/or F1 swim-up success, suggesting that developmental exposures to xenoestrogens may cause irreversible effects on egg quality and progeny even after depuration. In conclusion, these results suggest that environmentally relevant mixtures of NP and EE can produce additive or non-additive effects depending on the particular response being determined and the respective exposure concentrations of each chemical. Thus, it is recommended that caution be exercised in ecological risk assessments when assuming additivity in piscine responses to xenoestrogen mixtures.

Previous studies exposing fish to xenoestrogens have demonstrated vitellogenin (VTG) induction, delayed gametogenesis, altered sex distribution, and decreased reproductive performance, with a majority of those studies focusing on exposure to single chemicals. The objective of this study was to determine the effects of binary mixtures of a weak estrogen receptor agonist, nonylphenol (NP) and a potent estrogen receptor agonist, 17α-ethinylestradiol (EE) on sex distribution, gametogenesis, VTG induction, heat shock protein 70 (HSP70) expression and reproductive capacity in zebrafish (Danio rerio). Fish were exposed from 2 to 60 days post-hatch (dph) to nominal concentrations of 10 or 100 µg/l NP (NP10 or NP100, respectively), 1 or 10 ng/l EE (EE1 or EE10, respectively), 1 ng/l EE + 10 or 100 µg/l NP (EE1+NP10 or EE1+NP100, respectively), 10 ng/l EE + 10 or 100 µg/l NP (EE10+NP10 or EE10+NP100, respectively) or solvent control (0.01% acetone v/v) in a static-renewal system with replacement every 48h. At 60 dph, fish from each treatment were euthanized for histological examination of gonads, and whole body VTG and HSP70 levels. Remaining fish were reared in clean water until adulthood (240 dph) for breeding studies. In all EE10 exposure groups (EE10, EE10+NP10 and EE10+NP100), increasing NP concentration acted less than additively to the action of EE in terms of VTG induction at 60 dph. Similarly, a less than additivity of effect was observed with egg production, where EE1+NP100 exposure resulted in significantly more eggs produced per breeding trial than EE1 alone. Histological staging of oogenesis revealed suppressed gametogenesis in females at 60 dph. There were no differences among treatment groups in whole body HSP70 expression in 60 dph fish or in gonadal HSP70 expression in adult fish. Although there was no statistical evidence of non-additivity, breeding trials in adults revealed significant reductions in egg viability, egg hatchability and/or F1 swim-up success, suggesting that developmental exposures to xenoestrogens may cause irreversible effects on egg quality and progeny even after depuration. In conclusion, these results suggest that environmentally relevant mixtures of NP and EE can produce additive or non-additive effects depending on the particular response being determined and the respective exposure concentrations of each chemical. Thus, it is recommended that caution be exercised in ecological risk assessments when assuming additivity in piscine responses to xenoestrogen mixtures.

A ampla utilização de medicamentos, a falta de gerenciamento na produção e no descarte desses produtos, bem como a dificuldade na remoção de resíduos de fármacos das águas residuais durante as fases do tratamento de efluentes tem causado a liberação destes micropoluentes nos recursos hídricos. O cloridrato de fluoxetina, conhecido comercialmente como Prozac®, tem sido muito utilizado em diversos países. Estudos demonstram sua presença no meio ambiente e o potencial de danos que este fármaco pode causar à biota. Desta forma, este trabalho estudou uma tecnologia de tratamento (POA - Processo Oxidativo Avançado) utilizando-se radiação ionizante, proveniente de um acelerador de elétrons, para a degradação do fármaco cloridrato de fluoxetina em solução aquosa e na mistura com esgoto doméstico. Após a irradiação foram feitas análises químicas na solução aquosa do fármaco com Espectrofotometria UV/VIS, Cromatografia Líquida Ultra Rápida (detectores UV/VIS e fluorescência) e quantificação do Carbono Orgânico Total (COT). Também foram empregados ensaios de toxicidade aguda (Daphnia similis e Vibrio fischeri) e crônica (Ceriodaphnia dubia). A eficiência na degradação do fármaco foi superior a 98,00% na menor dose de radiação (0,5 kGy), porém houve baixa taxa de mineralização para as doses aplicadas neste estudo. Para a Daphnia similis na dose de 0,5 kGy houve eficiência de 83,75% na redução da toxicidade do cloridrato de fluoxetina e 87,24% para 5,0 kGy, houve eficiência de 100,00% na redução da toxicidade para o esgoto doméstico e para a mistura (CF + esgoto) 79,32% na dose de 5,0 kGy. A eficiência para a Vibrio fischeri foi de 17,26% (melhor eficiência na dose de 5,0 kGy) e após a correção do pH das amostras a melhor eficiência foi para 20,0 kGy (26,78%), para o esgoto e para a mistura as eficiências ficaram em torno dos 20,00% para todas as doses de radiação aplicadas. Em relação a toxicidade crônica para Ceriodaphnia dubia a eficiência foi de 97,50% para 5,0 kGy. Verificou-se que a Ceriodaphnia dubia possui maior sensibilidade ao fármaco, seguido da bactéria Vibrio fischeri e por fim a Daphnia similis. / Extensive use of drugs, lack of management in the production and disposal of these products as well as the difficulty in removing residues of pharmaceuticals during wastewater treatment phases imply the release of these micropollutants in water resources. Fluoxetine hydrochloride, known commercially as Prozac®, have been often used in many countries. Studies demonstrate their presence in the environment and potential damage that this drug may cause the biota. Therefore, this paper studied a treatment technology (AOP - Advanced Oxidative Process) using ionizing radiation from an electron accelerator, for the degradation of the drug fluoxetine hydrochloride in aqueous solution and mixed with domestic sewage. After irradiation at aqueous solution chemical analyzes at the drug were done using spectrophotometry UV/VIS, Ultra Fast Liquid Chromatography (detectors UV/ VIS and fluorescence) and quantification of Total Organic Carbon (TOC). Acute toxicity tests (Daphnia similis and Vibrio fischeri) and chronic (Ceriodaphnia dubia) were employed. The efficiency for the degradation of the drug was greater than 98.00% at the lowest absorbed dose of radiation (0.5 kGy), however there was low rate of mineralization to the doses applied in this study. The efficiency reduction of toxicity was 83.75% using Daphnia similis at 0.5 kGy of absorbed dose and 87.24% at 5.0 kGy to fluoxetine hydrochloride, efficiency was 100.00% in reducing toxicity to domestic sewage and the mixture (CF + sewage) was 79.32% at a dose of 5.0 kGy. The efficiency to Vibrio fischeri was 17.26% (better efficiency at the dose of 5.0 kGy) and after correction of pH to a better performance was 20.0 kGy (26.78%), for sewage and mixture efficiencies were about 20,00% for all doses of radiation applied. In relation to chronic toxicity effects to Ceriodaphnia dubia efficiency was 97.50% at 5.0 kGy. It was verified that Ceriodaphnia dubia is more sensitive to the drug, followed by the bacterium Vibrio fischeri and finally Daphnia similis.

A ampla utilização de medicamentos, a falta de gerenciamento na produção e no descarte desses produtos, bem como a dificuldade na remoção de resíduos de fármacos das águas residuais durante as fases do tratamento de efluentes tem causado a liberação destes micropoluentes nos recursos hídricos. O cloridrato de fluoxetina, conhecido comercialmente como Prozac®, tem sido muito utilizado em diversos países. Estudos demonstram sua presença no meio ambiente e o potencial de danos que este fármaco pode causar à biota. Desta forma, este trabalho estudou uma tecnologia de tratamento (POA - Processo Oxidativo Avançado) utilizando-se radiação ionizante, proveniente de um acelerador de elétrons, para a degradação do fármaco cloridrato de fluoxetina em solução aquosa e na mistura com esgoto doméstico. Após a irradiação foram feitas análises químicas na solução aquosa do fármaco com Espectrofotometria UV/VIS, Cromatografia Líquida Ultra Rápida (detectores UV/VIS e fluorescência) e quantificação do Carbono Orgânico Total (COT). Também foram empregados ensaios de toxicidade aguda (Daphnia similis e Vibrio fischeri) e crônica (Ceriodaphnia dubia). A eficiência na degradação do fármaco foi superior a 98,00% na menor dose de radiação (0,5 kGy), porém houve baixa taxa de mineralização para as doses aplicadas neste estudo. Para a Daphnia similis na dose de 0,5 kGy houve eficiência de 83,75% na redução da toxicidade do cloridrato de fluoxetina e 87,24% para 5,0 kGy, houve eficiência de 100,00% na redução da toxicidade para o esgoto doméstico e para a mistura (CF + esgoto) 79,32% na dose de 5,0 kGy. A eficiência para a Vibrio fischeri foi de 17,26% (melhor eficiência na dose de 5,0 kGy) e após a correção do pH das amostras a melhor eficiência foi para 20,0 kGy (26,78%), para o esgoto e para a mistura as eficiências ficaram em torno dos 20,00% para todas as doses de radiação aplicadas. Em relação a toxicidade crônica para Ceriodaphnia dubia a eficiência foi de 97,50% para 5,0 kGy. Verificou-se que a Ceriodaphnia dubia possui maior sensibilidade ao fármaco, seguido da bactéria Vibrio fischeri e por fim a Daphnia similis. / Extensive use of drugs, lack of management in the production and disposal of these products as well as the difficulty in removing residues of pharmaceuticals during wastewater treatment phases imply the release of these micropollutants in water resources. Fluoxetine hydrochloride, known commercially as Prozac®, have been often used in many countries. Studies demonstrate their presence in the environment and potential damage that this drug may cause the biota. Therefore, this paper studied a treatment technology (AOP - Advanced Oxidative Process) using ionizing radiation from an electron accelerator, for the degradation of the drug fluoxetine hydrochloride in aqueous solution and mixed with domestic sewage. After irradiation at aqueous solution chemical analyzes at the drug were done using spectrophotometry UV/VIS, Ultra Fast Liquid Chromatography (detectors UV/ VIS and fluorescence) and quantification of Total Organic Carbon (TOC). Acute toxicity tests (Daphnia similis and Vibrio fischeri) and chronic (Ceriodaphnia dubia) were employed. The efficiency for the degradation of the drug was greater than 98.00% at the lowest absorbed dose of radiation (0.5 kGy), however there was low rate of mineralization to the doses applied in this study. The efficiency reduction of toxicity was 83.75% using Daphnia similis at 0.5 kGy of absorbed dose and 87.24% at 5.0 kGy to fluoxetine hydrochloride, efficiency was 100.00% in reducing toxicity to domestic sewage and the mixture (CF + sewage) was 79.32% at a dose of 5.0 kGy. The efficiency to Vibrio fischeri was 17.26% (better efficiency at the dose of 5.0 kGy) and after correction of pH to a better performance was 20.0 kGy (26.78%), for sewage and mixture efficiencies were about 20,00% for all doses of radiation applied. In relation to chronic toxicity effects to Ceriodaphnia dubia efficiency was 97.50% at 5.0 kGy. It was verified that Ceriodaphnia dubia is more sensitive to the drug, followed by the bacterium Vibrio fischeri and finally Daphnia similis.

Persistent organic pollutants (POPs) cause significant effects on organisms due to their resistance to environmental degradation and specific toxic responses. Although POPs toxicities were linked to oxidative stress in the previous studies, there are few POPs studies that link them with oxidative stress in zebrafish during development. Aim of this study is to investigate effect of selected POPs on expression of genes involved in oxidative stress response and biotransformation of xenobiotics in zebrafish. Zebrafish embryos in 96 hours’ post-fertilization were exposed to selected POPs and their mixture. To explore the developmental toxicity in zebrafish early stage, we exposed 3,3',4,4',5-pentachlorobiphenyl (PCB), perfluorooctanesulfonic acid (PFOS) and perfluorohexanoic acid (PFHxA) at concentrations of 7.5 μg/L, 50 μM, 50 μM until 96 hours’ post-fertilization. The effects were measured by gene expression quantification technique - quantitative real-time PCR (qPCR). Significant up-regulation in gene expression was detected in embryos treated with mixture of PCB with PFHxA and PCB with PFOS only for cytochrome P450(cyp1a). The results also showed the treatment with selected compound caused significant higher upregulation of cyp1a when we compare the treatment in the individual compounds to the mixture compounds. However, treatments did not cause changes in expression of genes involved in oxidative stress response (glutathione peroxidase 1a(gpx1a), tumor protein p53(tp53), aryl hydrocarbon receptor 2 (ahr2)). The result also suggests that exposure to selected POPs in mixtures or alone is not causing oxidative stress in early stage of embryonal development of zebrafish but activating biotransformation function of the organism. Effect of activation of biotransformation capacity by means of cyp1a upregulation is also higher when POPs are in mixtures over when used as individual substance.

Bottom sediments around the world store large amounts of legacy hydrophobic organic contaminants (HOCs), forming mixtures of unknown chemical composition. Primary emissions to the environment of many HOCs have been reduced as a consequence of regulation. However, HOCs may be released from the sediments to water and biota, and there is therefore a risk of negative effects on local ecosystems. The activity of benthic organisms can enhance the sediment-to-water flux of HOCs, a process called bioturbation. Few in situ assessments of the sediment-to-water flux are available in the scientific literature, and the effect of bioturbation on the sediment-to-water flux of HOCs has not been studied in the field. Thus, there is a need to improve in situ methods for direct determination of sediments as a source of HOCs to water, and thereby include the effect of bioturbation. In Paper I, a benthic flow-through chamber was developed for environmentally realistic in situ assessments of the sediment-to-water flux. In Paper II, the sediment-to-water flux of polycyclic aromatic hydrocarbons (PAHs) was assessed using the flow-through chamber at four sites on the Swedish Baltic Sea coast. The sediments at all four sites acted as sources of PAHs to water. In the same study, potential effects of bioturbation, with an increase of the sediment-to-water flux by up to one order of magnitude, were observed at sites with bioturbating organisms. In the past, assessing the toxicity of HOCs has been challenging due to difficulties in maintaining stable exposure concentrations of the test chemical. In Paper III, a passive dosing method, where the test chemical partitions from a polymer (silicone) to the aquatic exposure medium, was developed and tested for chronic exposure. A stable exposure concentration could be maintained, and the chronic toxicity to the sediment-dwelling harpacticoid Nitocra spinipes of chronic exposure to triclosan was assessed in a 6-week population development test. In Paper IV, a passive sampling and dosing method was developed and used to assess the toxicity of an environmental chemical mixture of bioavailable sediment-associated HOCs transferred from a contaminated sediment to the laboratory-based bioassay. The passive sampling and dosing method can be used to assess the toxicity of environmental mixtures of chemicals at environmentally realistic concentrations to which ecosystems are constantly exposed. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

Amongst the polar organic compounds occurring in unrefined and refined crude oils and the associated polluted production waters, complex mixtures of acids, known historically as naphthenic acids (NAs), have achieved prominence. This is particularly because NAs have been designated a toxicant class of concern in the oil sands process-affected water (OSPW) that has accumulated in vast quantities following exploitation of the oil sands of Northern Alberta, Canada in recent years. However, though there have been calls for NAs to be added to pollutant inventories, at the initiation of the current study, little knowledge existed of the exact composition of refined or unrefined NAs. The overall aim of the current study was therefore to identify individual NAs in refined (commercial) and unrefined (e.g. oil sands process-derived) complex mixtures of acids and then to assess the toxicity of any identified NAs. Individual NAs were tentatively identified by interpretation of the electron ionisation mass spectra of methyl ester derivatives, following comprehensive multidimensional gas chromatography-mass spectrometry (GCxGC-MS). Reference acids were then either purchased, or more commonly, where they were not commercially-available, synthesised, mainly by micro-hydrogenation methods, for co-chromatography and comparison of mass spectra of methyl esters with those of unknowns. The synthetic NAs, purified to >97% were then subjected to toxicological assessments using the Microtox™ assay. In all, 34 compounds were obtained pure enough for testing. Microtox results revealed that the toxicity endpoint (50% Inhibition Concentration, IC50) was between 0.004 and 0.7 mM. Exponential and other correlations were noted between carbon number and toxicity in several of the structural groups of acids assayed, which may be beneficial for predictions of toxicity of non-synthesised acids. Although n-hexanoic acid (IC50 0.7 mM) had the lowest toxicity, adamantane-type acids were the least toxic as a group overall. Conversely, the decahydronaphthalene (decalin)-type acids had the largest range of toxicities (IC50 0.004 to 0.3 mM) and the most toxic acid assayed was 3-decalin-1-yl-propanoic acid. According to USEPA guidelines many individual acids can be said to show low to medium toxicity. Since the acids in commercial and unrefined NAs occur in complex mixtures, an attempt was also made to assess mixture toxicity. Mixtures of individual structural groups of acids (e.g. acyclic isoprenoid acids, n-acids) and a mixture of all 34 acids were assessed. Apart from the adamantane sub-group of acids, all of the mixtures showed toxicities lower than the sum of the parts when calculated using equations for Concentration Addition and Model Deviation Ratios (simply the predicted IC50/Observed IC50). A hypothesis that achievement of a critical micelle concentration is required to produce toxicity was proposed to explain the lower than expected results. Some of the mass spectra of NA present in the commercial and unrefined mixtures were inconsistent with those of any of the alicyclic acids synthesised or purchased. These were hypothesised to be aromatic acids. Fractionation experiments of the NA mixtures using silver ion thin layer chromatography and solid phase extraction (Ag+TLC and Ag+SPE) were carried out in order to provide further evidence for aromatic acids. Ag+TLC allowed separation of a methylated NA mixture from OSPW into three distinct fractions; Ag+SPE resulted in eleven fractions, through the use of a wider range of solvents and differential solvent ratios. Analysis of the fractions by GC-MS revealed that each fraction was largely still made up of unresolved acids (as esters), although one or two fractions revealed some resolved acids. Use of averaged mass spectra and mass chromatography on each fraction revealed further resolved chromatographic peaks and associated interpretable mass spectra. Each of eight of the eleven sub-fractions were examined by GC-MS, in some cases by GCxGC-MS, and all by infrared spectroscopy, ultraviolet visible spectrophotometry and elemental analysis. A number of structures were proposed for the aromatic acids, including those with sulphur-containing moieties. It was noted that far from being minor components, aromatic acids comprised ca.25-40% of the OSPW acid extracts.

Les pesticides de nouvelle génération sont le plus souvent épandus à de faibles doses et en mélange. Peu d’études se sont intéressées jusqu’à présent à l’effet de ces mélanges sur la biodégradation et la toxicité de chaque pesticide et/ou métabolite. Le but de ces travaux de thèse était d’étudier les voies de biotransformation de chacun des trois herbicides d’un mélange constitué de mésotrione (β-tricétone), nicosulfuron (sulfonylurée) et S-métolachlore (chloroacétanilide) utilisé sur les cultures de maïs, ainsi que la toxicité (test Microtox ® ) des herbicides et de leurs métabolites, seuls et en mélanges. L’identification des métabolites de la mésotrione chez la souche Bacillus megaterium Mes11 et une étude de protéomique différentielle ont suggéré l’implication de nitroréductases dans la première étape de la biotransformation de cet herbicide, rôle confirmé ensuite par la caractérisation structurelle et fonctionnelle de deux enzymes capables de transformer la mésotrione : les nitroréductases NfrA1 et NfrA2, appartenant à la sous-famille NfsA-FRP des Nitro-FMN réductases. La voie de biotransformation du nicosulfuron a, quant à elle, été étudiée chez la souche Pseudomonas fluorescens SG-1 isolée à partir de sol agricole, capable de transformer cet herbicide par co-métabolisme. Cette biotransformation conduit à la formation de deux métabolites majoritaires issus du clivage de la liaison sulfonylurée du nicosulfuron, l’un deux (l’ADMP, 2-amino-4,6-diméthoxypyrimidine) présentant une toxicité 20 fois supérieure à celle de la molécule mère. Nous avons également étudié qualitativement et quantitativement la biotransformation de la mésotrione et du nicosulfuron par la souche Mes11 séparément ou en mélange, et en présence ou non de S-métolachlore Les résultats ont montré un effet négatif de la mésotrione sur la biotransformation du nicosulfuron et un effet positif du S-métolachlore sur la biotransformation de la mésotrione. Tous les mélanges d’herbicides testés ont montré des effets synergiques pour la toxicité vis-à-vis de A. fischeri, tandis que les mélanges de métabolites (avec ou sans S-métolachlore) étaient majoritairement synergiques ou antagonistes. La dernière partie des travaux de thèse est focalisée sur le développement d’une technique préventive de traitement de la pollution par les pesticides d’origine agricole (bioprophylaxie). Nous avons fait la preuve de concept de cette technique par une étude en microcosmes de sol. L’épandage simultané de l’herbicide 2,4-D (acide 2,4-dichlorophénoxyacétique) et de la souche Cupriavidus necator JMP134 capable de le minéraliser a en effet permis de réduire le temps de demi-vie de ce composé d’un facteur 3, tout en conservant son activité herbicide. / The new-generation pesticides are often sprayed at low dosages and in mixtures. Up to now, a few studies focused on the effect of these mixtures on the biodegradation and the toxicity of each pesticide and/or metabolite. The aim of this Ph.D. work was to study the biotransformation of each herbicide of a mixture composed of mesotrione (β-triketone), nicosulfuron (sulfonylurea) and S-metolachlor (chloroacetanilide) applied on maize crops, as well as the toxicity (Microtox® test) of the herbicides/metabolites alone or in mixture. The identification of mesotrione metabolites by the strain Bacillus megaterium Mes11 and a differential proteomic approach suggested the role of nitroreductases in the first step of mesotrione biotransformation. This was confirmed by the structural and functional characterization of two enzymes able to biotransform mesotrione: the NfrA1 and NfrA2 nitroreductases, belonging to the NfsA-FRP sub-family of Nitro-FMN reductases. The biotransformation pathway of nicosulfuron has been elucidated for the strain Pseudomonas fluorescens SG-1 isolated from an agricultural soil and able to co-metabolically biotransform nicosulfuron. Two major metabolites resulting from the cleavage of the sulfonylurea bridge were identified, one of them (ADMP, 2-amino-4,6-dimethoxypyrimidine) presenting a 20-fold higher toxicity than the parent compound. The simultaneous biotransformation of mesotrione and nicosulfuron by the strain Mes11 was also qualitatively and quantitatively studied, showing a negative effect of mesotrione on nicosulfuron biotransformation, and a positive effect of S-metolachlor on mesotrione biotransformation. All parent compound mixtures tested resulted in synergistic effects towards A. fischeri, while metabolite mixtures (with or without S-metolachlor) were mostly synergistic or antagonistic. The last part of the PhD work was devoted to the development of a preventive technique for the treatment of pollutions caused by agricultural pesticides (bioprophylaxis). We made the proof of concept of this method by using a soil microcosm study. The simultaneous spreading of 2,4-D (2,4-dichlorophenoxyacetic acid) herbicide and the strain Cupriavidus necator JMP134 able to mineralize it allowed a 3-fold reduction of 2,4-D half-life in soil, while preserving its herbicide activity.

Pharmaka werden nach ihrer Einnahme bzw. Verabreichung über verschiedene Pfade in die Umwelt eingetragen. Obwohl Arzneimittel zu den toxikologisch best-untersuchten und -charakterisierten Stoffen gehören, ist ihre Wirkung auf die Umwelt und die darin lebenden Organismen weit weniger gut untersucht. Wenn in der Literatur Daten zur Ökotoxizität vorhanden sind, so beziehen sich diese meist nur auf die Wirkung von Einzelstoffen. In der Umwelt sind die Organismen jedoch gegenüber Mischungen exponiert. Aufgrund der geschilderten Problematik wurden eine Reihe von Arzneimitteln unterschiedlicher Indikationsgruppen einzeln und in Kombination mit dem Embryotest mit dem Zebrabärbling (Danio rerio, DarT) untersucht. Dieses Testsystem wurde durch Schulte &amp;amp; Nagel (1994) als Alternativmethode zum akuten Fischtest nach OECD 203 entwickelt und bietet den Vorteil neben letalen auch eine Reihe von subletalen Endpunkten erfassen zu können. Es handelt sich zudem nach dem deutschen Tierschutzgesetz nicht um einen Tierversuch. Die generelle Vergleichbarkeit der ermittelten Werte mit Daten aus akuten Fischtests nach OECD 203 sowie die Anwendbarkeit für verschiedenste Fragestellungen konnten in einer Reihe von Studien gezeigt werden (Nagel, 2002). Für die hier vorgestellten Untersuchungen wurden zunächst 32 Pharmaka und drei Pflanzenschutzmittel als Einzelstoffe mit dem DarT untersucht. Basierend auf den Ergebnissen der Einzelstofftests wurden Mischungen sowohl aus Substanzen mit ähnlichen als auch unähnlichen Wirkmechanismen getestet. Es zeigte sich, dass unabhängig vom Wirkmechanismus die Mischungstoxizität durch das Konzept der Konzentrationsadditivität gut vorhergesagt wurde, während das Konzept der Unabhängigen Wirkung die Mischungstoxizität unterschätzte. Ebenfalls konnte gezeigt werden, dass die Kombination der Stoffe auf Basis der NOEC, die im DarT anhand der Herzschlagfrequenz nach 48 Stunden ermittelt wird, zu deutlichen Mischungseffekten führt.

Pharmaka werden nach ihrer Einnahme bzw. Verabreichung über verschiedene Pfade in die Umwelt eingetragen. Obwohl Arzneimittel zu den toxikologisch best-untersuchten und -charakterisierten Stoffen gehören, ist ihre Wirkung auf die Umwelt und die darin lebenden Organismen weit weniger gut untersucht. Wenn in der Literatur Daten zur Ökotoxizität vorhanden sind, so beziehen sich diese meist nur auf die Wirkung von Einzelstoffen. In der Umwelt sind die Organismen jedoch gegenüber Mischungen exponiert. Aufgrund der geschilderten Problematik wurden eine Reihe von Arzneimitteln unterschiedlicher Indikationsgruppen einzeln und in Kombination mit dem Embryotest mit dem Zebrabärbling (Danio rerio, DarT) untersucht. Dieses Testsystem wurde durch Schulte &amp;amp; Nagel (1994) als Alternativmethode zum akuten Fischtest nach OECD 203 entwickelt und bietet den Vorteil neben letalen auch eine Reihe von subletalen Endpunkten erfassen zu können. Es handelt sich zudem nach dem deutschen Tierschutzgesetz nicht um einen Tierversuch. Die generelle Vergleichbarkeit der ermittelten Werte mit Daten aus akuten Fischtests nach OECD 203 sowie die Anwendbarkeit für verschiedenste Fragestellungen konnten in einer Reihe von Studien gezeigt werden (Nagel, 2002). Für die hier vorgestellten Untersuchungen wurden zunächst 32 Pharmaka und drei Pflanzenschutzmittel als Einzelstoffe mit dem DarT untersucht. Basierend auf den Ergebnissen der Einzelstofftests wurden Mischungen sowohl aus Substanzen mit ähnlichen als auch unähnlichen Wirkmechanismen getestet. Es zeigte sich, dass unabhängig vom Wirkmechanismus die Mischungstoxizität durch das Konzept der Konzentrationsadditivität gut vorhergesagt wurde, während das Konzept der Unabhängigen Wirkung die Mischungstoxizität unterschätzte. Ebenfalls konnte gezeigt werden, dass die Kombination der Stoffe auf Basis der NOEC, die im DarT anhand der Herzschlagfrequenz nach 48 Stunden ermittelt wird, zu deutlichen Mischungseffekten führt.