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  • 1.
    Gustavsson, Lillemor
    et al.
    Örebro University, Department of Natural Sciences.
    Klee, Nina
    Olsman, Helena
    Hollert, Henner
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Fate of Ah receptor agonists during biological treatment of an industrial sludge containing explosives and pharmaceutical residues2004In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 11, no 6, p. 379-386Article in journal (Refereed)
    Abstract [en]

    GOAL, SCOPE AND BACKGROUND:

    Sweden is meeting prohibition for deposition of organic waste from 2005. Since 1 million tons of sludge is produced every year in Sweden and the capacity for incineration does not fill the demands, other methods of sludge management have to be introduced to a higher degree. Two biological treatment alternatives are anaerobic digestion and composting. Different oxygen concentrations result in different microbial degradation pathways and, consequently, in a different quality of the digestion or composting residue, It is therefore necessary to study sludge treatment during different oxygen regimes in order to follow both degradation of compounds and change in toxicity. In this study, an industrial sludge containing explosives and pharmaceutical residues was treated with anaerobic digestion or composting, and the change in toxicity was studied. Nitroaromatic compounds, which are the main ingredients of both pharmaceutical and explosives, are well known to cause cytotoxicity and genotoxicity. However, little data are available concerning sludge with nitroaromatics and any associated dioxin-like activity. Therefore, we studied the sludge before and after the treatments in order to detect any changes in levels of Ah receptor (AhR) agonists using two bioassays for dioxin-like compounds.

    METHODS:

    An industrial sludge was treated with anaerobic digestion or composting in small reactors in a semi-continuous manner. The same volume as the feeding volume was taken out daily and stored at -20 degrees C. Sample preparation for the bioassays was done by extraction using organic solvents, followed by clean up with silica gel or sulphuric acid, yielding two fractions. The fractions were dissolved in DMSO and tested in the bioassays. The dioxin-like activity was measured using the DR-CALUX assay with transfected H4IIE rat hepatoma pGudluc cells and an EROD induction assay with RTL-W1 rainbow trout liver cells.

    RESULTS AND DISCUSSION:

    The bioassays showed that the sludge contained AhR agonists at levels of TCDD equivalents (TEQs) higher than other sludge types in Sweden. In addition, the TEQ values for the acid resistant fractions increased considerably after anaerobic digestion, resulting in an apparent formation of acid resistant TEQs in the anaerobic reactors. Similar results have been reported from studies of fermented household waste. There was a large difference in effects between the two bioassays, with higher TEQ levels in the RTL-W1 EROD assay than in the DR-CALUX assay. This is possibly due to a more rapid metabolism in rat hepatocytes than in trout hepatocytes or to differences in sensitivities for the AhR agonists in the sludge. It was also demonstrated by GC/FID analysis that the sludge contained high concentrations of nitroaromatics. It is suggested that nitroaromatic metabolites, such as aromatic amines and nitroanilines, are possible candidates for the observed bioassay effects. It was also found that the AhR agonists in the sludge samples were volatile.

    CONCLUSIONS:

    The sludge contained fairly high concentrations of volatile AhR agonists. The increase of acid resistant AhR agonist after anaerobic digestion warrants further investigations of the chemical and toxic properties of these compounds and of the mechanisms behind this observation.

    RECOMMENDATION AND OUTLOOK:

    This study has pointed out the benefits of using different types of mechanism-specific bioassays when evaluating the change in toxicity by sludge treatment, in which measurement of dioxin-like activity can be a valuable tool. In order to study the recalcitrant properties of the compounds in the sludge using the DR-CALUX assay, the exposure time can be varied between 6 and 24 hours. The properties of the acid-resistant AhR agonists formed in the anaerobic treatment have to be investigated in order to choose the most appropriate method for sludge management.

  • 2.
    Hagberg, Jessika
    et al.
    Örebro University, Department of Natural Sciences.
    Olsman, Helena
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Chemical and toxicological characterisation of PBDFs from photolytic decomposition of decaBDE in tolueneManuscript (Other academic)
  • 3.
    Hagberg, Jessika
    et al.
    Örebro University, Department of Natural Sciences.
    Olsman, Helena
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Lindström, Gunilla
    Örebro University, Department of Natural Sciences.
    Chemical and toxicological characterisation of PBDFs from photolytic decomposition of decaBDE in toluene2006In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 32, no 7, p. 851-857Article in journal (Refereed)
    Abstract [en]

    A substantial formation of PBDF congeners was observed during photolytic decomposition of decaBDE in toluene. The decaBDE degradation was monitored by chemical and toxicological analysis and in all, twenty-seven mono- to hexasubstituted polybrominated dibenzofurans (PBDFs) were detected in toluene solutions of decabromodiphenyl ether (decaBDE) after irradiation with UV-A, UV-AB and UV-ABC. The concentration levels of PBDFs formed after 16 h of UV exposure increased with wider spectra and were determined to be 3.5, 4.2 and 14 microg/ml after UV-A, UV-AB and UV-ABC irradiation, respectively. In accordance, bioassay derived TEQs (bio-TEQs), determined with the DR-CALUX assay, increased with a similar pattern. The PBDFs formed after the three UV exposures accounted for 0.31%, 0.35% and 1.2% of the initial amount of decaBDE (molar basis). The PBDF congener patterns were consistent in all three UV experiments which imply that no alterations were induced in the PBDF formation or degradation processes due to differences in UV irradiation. However, these processes tended to increase with wider spectra and increasing radiation energy most likely due to the strong absorbance of for example decaBDE at shorter wavelengths. After total decaBDE decomposition the PBDF formation increased significantly in the UV-ABC experiment. The tetra to hexasubstituted BDFs constituted the majority of detected compounds in all experiments. In all samples, the estimated chemical TEQ indicate that the bio-TEQs observed are largely explained by the presence of non-2,3,7,8-substituted PBDFs with relatively low toxicological potencies.

  • 4. Hinger, Gunnar
    et al.
    Brinkmann, Markus
    Bluhm, Kerstin
    Sagner, Anne
    Takner [Olsman], Helena
    Örebro University, School of Science and Technology.
    Eisentraeger, Adolf
    Braunbeck, Thomas
    Engwall, Magnus
    Örebro University, School of Science and Technology.
    Tiehm, Andreas
    Hollert, Henner
    Some heterocyclic aromatic compounds are Ah receptor agonists in the DR-CALUX assay and the EROD assay with RTL-W1 cells2011In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 18, no 8, p. 1297-1304Article in journal (Refereed)
    Abstract [en]

    Purpose Heterocyclic aromatic compounds containing nitrogen, sulfur, or oxygen heteroatoms (NSO-HET) have been detected in air, soil, marine, and freshwater systems. However, only few publications are available investigating NSO-HET using in vitro bioassays. To support better characterization of environmental samples, selected NSO-HET were screened for dioxin-like activity in two bioassays. Methods The present study focuses on the identification and quantification of dioxin-like effects of 12 NSO-HET using the DR-CALUX assay, and the 7-ethoxyresorufin-O-deethylase (EROD) assay with the permanent fish liver cell line RTL-W1. Changes of the total medium compound concentrations during the test procedure due to, e.g., sorption or volatilization were quantified using GC/MS. Results The NSO-HET benzofuran, 2,3-dimethylbenzofuran, dibenzofuran, dibenzothiophen, acridine, xanthene, and carbazole caused a response in the DR-CALUX assay. Only benzofuran and 2,3-dimethylbenzofuran were also positive in the EROD assay. All other compounds were inactive in the EROD assay. Relative potency (REP) values ranged from (2.80 +/- 1.32) center dot 10(-8) to (3.26 A +/- 2.03) A center dot 10(-6) in the DR-CALUX and from (3.26 A +/- 0.91) A center dot 10(-7) to (4.87 A +/- 1.97) A center dot 10(-7) in the EROD assay. Conclusions The REP values were comparable to those of larger polycyclic aromatic hydrocarbons, e.g., fluoranthene and pyrene. Thus, and because of the ubiquitous distribution of heterocyclic aromatic compounds in the environment, the provided data will further facilitate the bioanalytical and analytical characterization of environmental samples towards these toxicants.

  • 5.
    Hollert, Henner
    et al.
    Department of Zoology, University of Heidelberg, Im Neuenheimer Feld 230, Heidelberg, Germany .
    Dürr, M.
    Department of Hygiene, Halle, Germany .
    Olsman, Helena
    Örebro University, School of Science and Technology.
    Halldin, Krister
    Department of Environmental Toxicology, Uppsala, Sweden .
    van Bavel, Bert
    Örebro University, School of Science and Technology. Department of Chemistry, Environmental Chemistry, Umeå, Sweden .
    Brack, W.
    UFZ Centre for Environmental Research Leipzig-Halle, Leipzig, Germany .
    Tysklind, M.
    Department of Environmental Toxicology, Uppsala, Sweden .
    Engwall, Magnus
    Örebro University, School of Science and Technology.
    Braunbeck, T.
    Department of Hygiene, Halle, Germany .
    Biological and chemical determination of dioxin-like compounds in sediments by means of a sediment triad approach in the catchment area of the River Neckar2002In: Ecotoxicology, ISSN 0963-9292, E-ISSN 1573-3017, Vol. 11, no 5, p. 323-336Article in journal (Refereed)
    Abstract [en]

    To evaluate the sediment quality of selected sites in the catchment area of the River Neckar, an integrative assessment approach was used to assess the ecological hazard potential of dioxin-like sediment compounds. The approach is based on 7-ethoxyresorufin-O-deethylase (EROD) induction in embryonic chicken liver culture and comprehensive chemical analyses of polycyclic aromatic hydrocarbons (priority PAHs according to the US Environmental Protection Agency). The majority of the sediment extracts exhibited high potencies as EROD-inducers. In one sediment sample, which was influenced by a sewage treatment plant, a very high concentration of 930 ng bioassay 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents (bio-TEQs)/g organic carbon could be determined. However, in none of the samples, more than 6% of the EROD-inducing potency could be explained by the PAHs analyzed chemically. Thus, non-analyzed compounds with EROD-inducing potency were present in the extracts. A fractionation of sediment samples according to pH allowed to localize the major part of EROD-inducing compounds in the neutral fractions. However, a significant portion of the EROD induction could also be explained by the acidic fractions. Following the concept of the Sediment Quality Triad according to Chapman, in situ alterations of macrozoobenthos were examined. A comparison of the results predicted by the EROD assay and chemical analyses with alterations in situ, as measured by means of the saprobic index and the ecotoxicological index according to Carmargo, revealed a high ecological relevance of the results of bioassays and chemical analyses for major sites.

  • 6. Hollert, Henner
    et al.
    Keiter, Steffen
    Böttcher, Melanie
    Grund, Steffi
    Seitz, Nadja
    Otte, Jens
    Bluhm, Kerstin
    Wurm, Karl
    Hecker, Markus
    Higley, Eric
    Giesy, John
    Takner [Olsman], Helena
    van Bavel, Bert
    Örebro University, School of Science and Technology.
    Engwall, Magnus
    Örebro University, School of Science and Technology.
    Reifferscheid, Georg
    Manz, Werner
    Erdinger, Lother
    Schulze, Tobias
    Luebcke-van Varel, Urte
    Kammann, Ulrike
    Schöneberger, René
    Suter, Marc
    Brack, Werner
    Strähle, Uwe
    Braunbeck, Thomas
    Eine Weight-of-Evidence-Studie zur Bewertung der Sedimentbelastung und des Fischrückgangs in der Oberen Donau [Assessing sediments and fish health using a weight-of-evidence approach : in search for the causes of fish decline in the Danube river]2009In: Umweltwissenschaften und Schadstoff-Forschung, ISSN 0934-3504, E-ISSN 1865-5084, Vol. 21, no 3, p. 260-263Article in journal (Refereed)
    Abstract [en]

    Background and aim Despite intensive and continuous stocking and improvement of water quality since the 1970s, fish populations, especially those of the grayling (Thymallus thymallus), have declined over the last two decades in the upper Danube River (Germany). In order to assess 1) possible links between molecular/biochemical responses and ecologically relevant effects, and 2) if ecotoxicological effects might be related to the decline in fish catches in the upper Danube river, sediment samples and fish were collected at different locations and analyzed using a weight-of-evidence (WOE) approach with several lines of evidence. The objective of the presentation is to introduce the conceptual framework and to review results of the ongoing study. As previously addressed by Chapman and Hollert (2006) a variety of lines of evidence can be used in WOE studies. Briefly, 1) a comprehensive battery of acute and mechanism-specific bioassays was used to characterize the ecotoxicological hazard potential. 2) Histopathological investigations and the micronucleus assay with erythrocytes were applied, analyzing in situ parameters. 3) Diversity and abundance of benthic macroinvertebrates and fish as well as 4) persistent organic pollutants, endocrine disrupting substances, limnochemical parameters and the concentration of heavy metals were recorded. To identify organic contaminants a spotential causes of sediment toxicity assays, 5) effect directed analysis was applied. © 2009 Springer-Verlag.

  • 7.
    Kalbin, Georgi
    et al.
    Örebro University, Department of Natural Sciences.
    Li, Shaoshan
    Örebro University, Department of Natural Sciences.
    Olsman, Helena
    Örebro University, Department of Natural Sciences.
    Pettersson, Mikael
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Effects of UV-B in biological and chemical systems: equipment for wavelength dependence determination2005In: Journal of Biochemical and Biophysical Methods, ISSN 0165-022X, E-ISSN 1872-857X, Vol. 65, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    The thinning of the stratospheric ozone layer has prompted a large number of studies of UV-B-induced effects in biological and chemical systems. The wavelength dependency of such effects is of interest from mechanistic, physiological or economic points of view. Here, we describe an apparatus for determining the wavelength dependency of UV-B effects in biological and chemical systems. The apparatus consists of a high intensity UV radiation source and narrow bandpass filters to produce UV radiation in even intervals (between 280 and 360 nm). The usefulness of the equipment is demonstrated in two different systems: 1) Chalcone synthase (CHS) gene is up-regulated by UV-B radiation. Therefore quantitative analysis of the CHS gene expression was chosen in the present investigation for studies of the wavelength dependency of gene expression regulation in plants. Maximum induction of CHS expression was found at 300 nm with a 12-fold induction compared with the control; 2) The wavelength dependency of formation of dioxin-like photoproducts from the brominated flame retardant decabrominated diphenyl ether (DeBDE) is described. This is an example of UV-B-induced conversion of non-toxic species into a number of products of which some may be toxic in the environment. In the UV interval studied, the highest dioxin-like activity was found in the sample irradiated at 330 nm and therefore this wavelength is most important for the mechanism involved in photoconversion of DeBDE.

  • 8. Keiter, Steffen
    et al.
    Grund, Stefanie
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Hagberg, Jessika
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Kammann, Ulrike
    Klempt, Martin
    Manz, Werner
    Olsman Takner, Helena
    Örebro University, Department of Natural Sciences.
    Braunbeck, Thomas
    Hollert, Henner
    Activities and identification of aryl hydrocarbon receptor agonists in sediments from the Danube river2008In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 390, no 8, p. 2009-2019Article in journal (Refereed)
    Abstract [en]

    This study is a consequence of a distinct fish decline in the Danube river since the beginning of the 1990s. In contrast to the decline of fish population, former studies have repeatedly documented that the water quality along the Danube river is improving. However, the conclusion of a pilot study in 2002 was that a high hazard potential is associated with local sediments. The present study documents that sediment samples from the Danube river showed comparatively high aryl hydrocarbon receptor mediated activity in biotests, using the cell lines GPC.2D.Luc, H4IIE (DR-CALUX®) and RTL-W1. The combination of chemical analysis, fractionation techniques and different in vitro tests revealed that priority pollutants could not explain the main induction, even though the concentrations of priority polycyclic aromatic hydrocarbons (PAHs) were very high (maximum in the tributary Schwarzach, sum of 16 EPA PAHs 26 μg/g). In conclusion, this investigation shows that nonpriority pollutants mainly mediate the high induction rates. Nevertheless, owing to the effects of PAHs towards fish and the connection between dioxin-like activity and carcinogenicity, the link between contamination and the fish population decline cannot be ruled out.

  • 9.
    Keiter, Steffen
    et al.
    University of Heidelberg, Heidelberg, Germany.
    Grund, Stefanie
    University of Heidelberg, Heidelberg, Germany.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Hagberg, Jessika
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Ulrike, Kammann
    Federal Research Centre for Fisheries, Hamburg, Germany.
    Klempt, Martin
    Federal Research Centre for Nutrition and Food, Hamburg, Germany.
    Manz, Werner
    Federal Institute of Hydrology, Koblenz, Germany.
    Olsman, Helena
    Örebro University, Department of Natural Sciences.
    Braunbeck, Thomas
    University of Heidelberg, Heidelberg, Germany.
    Hollert, Henner
    RWTH Aachen University, Aachen, Germany .
    Activities and identification of aryl hydrocarbon receptor agonists in sediments from the Danube river2008In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 390, no 8, p. 2009-2019Article in journal (Refereed)
    Abstract [en]

    This study is a consequence of a distinct fishdecline in the Danube river since the beginning of the 1990s. In contrast to the decline of fish population, former studies have repeatedly documented that the water quality along the Danube river is improving. However, the conclusion of a pilot study in 2002 was that a high hazard potentialis associated with local sediments. The present study documents that sediment samples from the Danube river showed comparatively high aryl hydrocarbon receptor mediated activity in biotests, using the cell lines GPC.2D.Luc, H4IIE(DR-CALUX®) and RTL-W1. The combination of chemical analysis, fractionation techniques and different in vitro tests revealed that priority pollutants could not explain the main induction, even though the concentrations of prioritypolycyclic aromatic hydrocarbons (PAHs) were very high (maximum in the tributary Schwarzach, sum of 16 EPAPAHs 26 μg/g). In conclusion, this investigation shows that nonpriority pollutants mainly mediate the high inductionrates. Nevertheless, owing to the effects of PAHs towards fish and the connection between dioxin-like activity andcarcinogenicity, the link between contamination and the fish population decline cannot be ruled out.

  • 10.
    Olsman, Helena
    Örebro University, Department of Natural Sciences.
    Bioassay analysis of dioxin-like compounds: response interactions and environmental transformation of Ah receptor agonists2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dioxin-like compounds mediate their toxicity by binding to the aryl hydrocarbon receptor (AhR) and through this receptor a cascade of biochemical and toxic events are triggered. Mechanism-specific dioxin bioassays utilise the AhR coupled induction of endogenous CYP1A proteins or reporter gene systems for detection of dioxin-like compounds and other AhR ligands. The use of mechanism-specific in vitro bioassays as a complement or alternative to conventional GC-MS analysis of dioxin-like compounds has gained acceptance over the last years and is also in part a search for a tool for rapid and facilitated dioxin risk assessment.

    This thesis includes several applications for bioassay analysis using the two bioassays Dioxin Responsive Chemically Activated Luciferase eXpression assay (DR-CALUX) and Chick Embryo Liver Culture Assay for Dioxins (CELCAD). The two dioxin bioassays were used to study the AhR mediated induction for single compounds, as well as for mixtures of AhR active compounds in different sample matrices, also including studies of the influence of clean-up methods and fractionation on bioassay response.

    Bioanalysis gave valuable information on the toxicological relevance of decaBDE UV photoproducts. The bioassay methodology was able to reflect the actual variation in PBDF formation, and enabled a good estimation of toxicity of the congeners formed, regardless of chemical identification and congener specific potency data. The congeners formed had low potencies compared to the most toxic 2,3,7,8-substituted congeners, but the high concentrations resulted in considerable levels of TEQs.

    For complex samples like organic household waste digestates it is advisable to use both bio- and chemical analysis, for confirmation of results, as far as possible. The bioassay-directed fractionation approach requires several fractionation steps (i.e. different methods) in order to obtain well-defined fractions, from which detailed conclusions can be drawn.

    Also, proper analysis of human adipose tissue, although by far less complex than organic household waste, requires fractionation. Bioanalysis of these samples showed large deviations from the additivity assumption applied in the TEF calculation from chemical analysis. Thus, it is not clear how to interpret the bioassay results in relation to chemical results, although both methods gave the same information on relative levels of AhR agonists and showed good reproducibility.

    Both DR-CALUX and CELCAD proved to be useful for AhR agonist analysis in mixtures and for single compounds. The DR-CALUX enables more rapid analysis of large number of samples and is therefore, a more suitable tool for AhR agonist detection, whereas CELCAD has more limitations and is more suitable for the study of AhR mediated toxicity with special emphasis on avian species. In vitro bioassays have many implications for the analysis of AhR agonists, yielding reliable and reproducible results, provided that proper clean-up and fractionation of samples is applied. Bioassays enable fast determinations of total or integrated effects of AhR ligands in samples, as well as specific potency studies. Thus, bioassays are in all a valuable and necessary complement to chemical analysis.

    List of papers
    1. Fractionation and determination of Ah receptor (AhR) agonists in organic waste after anaerobic biodegradation and in batch experiments with PCB and decaBDE
    Open this publication in new window or tab >>Fractionation and determination of Ah receptor (AhR) agonists in organic waste after anaerobic biodegradation and in batch experiments with PCB and decaBDE
    Show others...
    (English)Manuscript (Other academic)
    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-2934 (URN)
    Available from: 2005-11-04 Created: 2005-11-04 Last updated: 2017-10-18Bibliographically approved
    2. Ah receptor agonists in UV-exposed toluene solutions of decabromodiphenyl ether (decaBDE) and in soils contaminated with polybrominated diphenyl ethers (PBDEs)
    Open this publication in new window or tab >>Ah receptor agonists in UV-exposed toluene solutions of decabromodiphenyl ether (decaBDE) and in soils contaminated with polybrominated diphenyl ethers (PBDEs)
    Show others...
    2006 (English)In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 13, no 3, p. 161-169Article in journal (Refereed) Published
    Abstract [en]

    GOAL, SCOPE AND BACKGROUND: The use of polybrominated diphenyl ethers (PBDEs) as flame retardants increases the risk for emissions of other brominated compounds, such as polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). The large homology in structure of PBDD/Fs and mechanism of toxic action, i.e. the capacity to activate the Ah receptor (AhR) pathway, compared to their well-studied chlorinated analogues, justifies a raised concern to study the environmental levels and fate of these compounds. Decabromodiphenyl ether (decaBDE) is the most widely used PBDE today. Studies on photolytic debromination of decaBDE in organic solvents have shown debromination of decaBDE, as well as formation of PBDFs. However, little is known about the transformation mechanisms and there are only scarce data on photoproducts and PBDE transformation in environmentally relevant matrices. In this study, mechanism-specific dioxin bioassays were used to study photolytic formation of AhR agonists in toluene solutions of decaBDE. In addition, the influence of irradiation time and UV-light wavelength on the formation was studied. PBDE congener patterns and presence of PBDD/Fs were analysed. Further, AhR agonists were analysed in agricultural soils contaminated with PBDEs. Soils were also exposed to UV-light to study changes in AhR agonist levels. METHODS: Toluene solutions of decaBDE were irradiated using three different spectra of UV-light, simulating UV-A (320-400 nm), UV-AB (280-400 nm), and UV-ABC (250-400 nm). Additionally, decaBDE solutions were exposed to narrow wavelength intervals (10 nm bandwidth) with the central wavelengths 280, 290, 300, 310, 320, 330, 340, 350, 360 nm. AhR agonists in decaBDE solutions were analysed with two different bioassays, the chick embryo liver-cell assay for dioxins (Celcad) and the dioxin responsive, chemically activated luciferase expression assay (DR-Calux). Also, the decaBDE solutions were analysed with LRGC-LRMS to obtain PBDE congener patterns for breakdown of decaBDE, and with HRGC-HRMS, for presence of PBDD/Fs. Four soils were exposed to UV-AB light, under both dry and moist conditions. Levels of AhR agonists in soil extract fractions, before and after UV-exposure, were analysed with the DR-Calux. RESULTS AND DISCUSSION: Significant levels of photoproducts able to activate the AhR pathway, up to 31 ng bio-TEQ/ml, were formed in UV-exposed decaBDE solutions. The transformation yield of decaBDE into AhR agonists was estimated to be at the 0.1%-level, on a molar basis. The net formation was highly dependent on wavelength, with the sample irradiated at 330 nm showing the highest level of dioxin-like activity. No activity was detected in controls. PBDE analysis confirmed decaBDE degradation and a clear time-dependent pattern for debromination of PBDE congeners. AhR agonist effect in the recalcitrant fractions of the soils corresponded to the levels of chemically derived TEQs, based only on chlorinated dioxin-like compounds in an earlier study. It was concluded that no significant levels of other AhR agonists, e.g. PBDFs, were accumulated in the soil. UV-light caused changes in AhR-mediated activity in the more polar and less persistent fractions of the soils, but it is not known which compounds are responsible for this. RECOMMENDATIONS AND PERSPECTIVES: The laboratory experiments in this study show that high levels of AhR agonists can be formed as photoproducts of decaBDE and it is important to elucidate if and under which conditions this might occur in nature. However, soil analysis indicates that photoproducts of PBDE do not contribute to the accumulated levels of persistent dioxin-like compounds in agricultural soil. Still, more data is needed to fully estimate the environmental importance of PBDE photolysis and occurrence of its photoproducts in other environmental compartments. Analysis with dioxin bioassays enabled us to gather information about photoproducts formed from decaBDE even though the exact identities of these compounds were not known. CONCLUSION: Bioassays are valuable for studying environmental transformation processes like this, where chemical analysis and subsequent toxicological evaluation requires available standard compounds and information on toxicological potency. The use of bioassays allows a rapid evaluation of toxicological relevance.

    Keywords
    Animals, Biological Assay, Cell Line; Tumor, Chick Embryo, Flame Retardants/radiation effects/toxicity, Phenyl Ethers/*chemistry/radiation effects/toxicity, Photolysis, Polybrominated Biphenyls/*chemistry/radiation effects/toxicity, Rats, Receptors; Aryl Hydrocarbon/*agonists, Soil Pollutants/radiation effects/toxicity, Solutions, Spectrometry; Mass; Electrospray Ionization, Toluene/chemistry, Ultraviolet Rays
    National Category
    Biological Sciences Chemical Sciences
    Research subject
    Biology; Chemistry
    Identifiers
    urn:nbn:se:oru:diva-4132 (URN)10.1065/espr2005.08.280 (DOI)16758706 (PubMedID)
    Available from: 2008-11-12 Created: 2008-11-12 Last updated: 2017-12-14Bibliographically approved
    3. Chemical and toxicological characterisation of PBDFs from photolytic decomposition of decaBDE in toluene
    Open this publication in new window or tab >>Chemical and toxicological characterisation of PBDFs from photolytic decomposition of decaBDE in toluene
    (English)Manuscript (Other academic)
    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-2936 (URN)
    Available from: 2005-11-04 Created: 2005-11-04 Last updated: 2017-10-18Bibliographically approved
    4. Differences in Ah receptor mediated response for eighteen polybrominated and mixed halogenated dibenzo-p-dioxins and -furans in cell lines from four different species
    Open this publication in new window or tab >>Differences in Ah receptor mediated response for eighteen polybrominated and mixed halogenated dibenzo-p-dioxins and -furans in cell lines from four different species
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    (English)Manuscript (Other academic)
    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-2937 (URN)
    Available from: 2005-11-04 Created: 2005-11-04 Last updated: 2017-10-18Bibliographically approved
    5. CALUX-TEQs, PCDD/F and PCB in SFE-extracts of human adipose tissue from breast cancer patients
    Open this publication in new window or tab >>CALUX-TEQs, PCDD/F and PCB in SFE-extracts of human adipose tissue from breast cancer patients
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    (English)Manuscript (Other academic)
    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-2938 (URN)
    Available from: 2005-11-04 Created: 2005-11-04 Last updated: 2017-10-18Bibliographically approved
  • 11.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Hagberg, Jessika
    Örebro University, Department of Natural Sciences.
    Kalbin, Georgi
    Örebro University, Department of Natural Sciences.
    Julander, Anneli
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Tysklind, Mats
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Ah receptor agonists in UV-exposed toluene solutions of decabromodiphenyl ether (decaBDE) and in soils contaminated with polybrominated diphenyl ethers (PBDEs)2006In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 13, no 3, p. 161-169Article in journal (Refereed)
    Abstract [en]

    GOAL, SCOPE AND BACKGROUND: The use of polybrominated diphenyl ethers (PBDEs) as flame retardants increases the risk for emissions of other brominated compounds, such as polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). The large homology in structure of PBDD/Fs and mechanism of toxic action, i.e. the capacity to activate the Ah receptor (AhR) pathway, compared to their well-studied chlorinated analogues, justifies a raised concern to study the environmental levels and fate of these compounds. Decabromodiphenyl ether (decaBDE) is the most widely used PBDE today. Studies on photolytic debromination of decaBDE in organic solvents have shown debromination of decaBDE, as well as formation of PBDFs. However, little is known about the transformation mechanisms and there are only scarce data on photoproducts and PBDE transformation in environmentally relevant matrices. In this study, mechanism-specific dioxin bioassays were used to study photolytic formation of AhR agonists in toluene solutions of decaBDE. In addition, the influence of irradiation time and UV-light wavelength on the formation was studied. PBDE congener patterns and presence of PBDD/Fs were analysed. Further, AhR agonists were analysed in agricultural soils contaminated with PBDEs. Soils were also exposed to UV-light to study changes in AhR agonist levels. METHODS: Toluene solutions of decaBDE were irradiated using three different spectra of UV-light, simulating UV-A (320-400 nm), UV-AB (280-400 nm), and UV-ABC (250-400 nm). Additionally, decaBDE solutions were exposed to narrow wavelength intervals (10 nm bandwidth) with the central wavelengths 280, 290, 300, 310, 320, 330, 340, 350, 360 nm. AhR agonists in decaBDE solutions were analysed with two different bioassays, the chick embryo liver-cell assay for dioxins (Celcad) and the dioxin responsive, chemically activated luciferase expression assay (DR-Calux). Also, the decaBDE solutions were analysed with LRGC-LRMS to obtain PBDE congener patterns for breakdown of decaBDE, and with HRGC-HRMS, for presence of PBDD/Fs. Four soils were exposed to UV-AB light, under both dry and moist conditions. Levels of AhR agonists in soil extract fractions, before and after UV-exposure, were analysed with the DR-Calux. RESULTS AND DISCUSSION: Significant levels of photoproducts able to activate the AhR pathway, up to 31 ng bio-TEQ/ml, were formed in UV-exposed decaBDE solutions. The transformation yield of decaBDE into AhR agonists was estimated to be at the 0.1%-level, on a molar basis. The net formation was highly dependent on wavelength, with the sample irradiated at 330 nm showing the highest level of dioxin-like activity. No activity was detected in controls. PBDE analysis confirmed decaBDE degradation and a clear time-dependent pattern for debromination of PBDE congeners. AhR agonist effect in the recalcitrant fractions of the soils corresponded to the levels of chemically derived TEQs, based only on chlorinated dioxin-like compounds in an earlier study. It was concluded that no significant levels of other AhR agonists, e.g. PBDFs, were accumulated in the soil. UV-light caused changes in AhR-mediated activity in the more polar and less persistent fractions of the soils, but it is not known which compounds are responsible for this. RECOMMENDATIONS AND PERSPECTIVES: The laboratory experiments in this study show that high levels of AhR agonists can be formed as photoproducts of decaBDE and it is important to elucidate if and under which conditions this might occur in nature. However, soil analysis indicates that photoproducts of PBDE do not contribute to the accumulated levels of persistent dioxin-like compounds in agricultural soil. Still, more data is needed to fully estimate the environmental importance of PBDE photolysis and occurrence of its photoproducts in other environmental compartments. Analysis with dioxin bioassays enabled us to gather information about photoproducts formed from decaBDE even though the exact identities of these compounds were not known. CONCLUSION: Bioassays are valuable for studying environmental transformation processes like this, where chemical analysis and subsequent toxicological evaluation requires available standard compounds and information on toxicological potency. The use of bioassays allows a rapid evaluation of toxicological relevance.

  • 12.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Hollert, Henner
    Kammann, Ulrike
    Klempt, Martin
    Otte, Jens
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Differences in Ah receptor mediated response for eighteen polybrominated and mixed halogenated dibenzo-p-dioxins and -furans in cell lines from four different speciesManuscript (Other academic)
  • 13.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Schnurer, Anna
    Bjornfoth, Helen
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Fractionation and determination of Ah receptor (AhR) agonists in organic waste after anaerobic biodegradation and in batch experiments with PCB and decaBDE2007In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 14, no 1, p. 36-43Article in journal (Refereed)
    Abstract [en]

    Goals, Scope and Background. Anaerobic digestion of organic household waste can lead to an increase in dioxin-like content, as determined by dioxin-specific bioassays. This may be a result of bioactivation of Ah receptor (AhR) agonists into more potent congeners. Work towards identifying the contributing compound groups is important in order to understand the mechanisms and to assess the relevance behind this increase in dioxin-like toxicity, since the residue can be used as a soil fertilising agent. The aim with the present work was to identify compound groups with AhR agonistic properties that caused the previously reported increase in dioxin-like activity after anaerobic biodegradation Methods. Firstly, chemical fractionation combined with dioxin bioassay testing was used to find bioactive classes of compounds. Secondly, batch digestion experiments with an externally added polychlorinated biphenyl (PCB) mixture (Clophen A50) and with decabrominated diphenyl ether (decaBDE), respectively, were studied as a possible process for transformation of precursors into more potent, dioxin-like compounds. Mesophilic (37 degrees C) and thermophilic (55 degrees C) anaerobic digestion were studied. Two different dioxin-specific bioassays were used to analyse AhR agonists in the biodegraded material, the CELCAD and the DR-CALUX. Results and Discussion. AhR agonist activity was detected in both di- and polyaromatic fractions of digestate extracts, which indicated that a diverse mixture of compounds contributed to the bioassay responses. No quantifiable activities were induced by the monoaromatic fractions. Further fractionation based on planarity revealed higher concentrations of AhR agonists than what was detected after the first fractionation, probably due to non-additive biological interactions of compounds in the extract that were removed in the second fractionation. These results showed significant activity in the non-planar diaromatic fractions and in the coplanar fractions of both diaromates and polyaromates. In the batch experiment with externally added PCB, an increase in dioxin-like activity was seen after 21 days of digestion at mesophilic conditions. After completed digestion, the content of AhR agonists was equal to the start concentration. PCB analysis with GC-MS indicated that dehalogenation of PCBs occurred in the digestors. The batch experiment with decaBDE showed no significant changes in TEQ-concentrations over time. Conclusions. The results show that the previously reported increase of AhR agonists during mesophilic anaerobic digestion is probably due to an accumulation of several different groups of AhR agonists, both diaromatic and polyaromatic, and both coplanar and non-planar. Batch experiments with externally added PCBs and decaBDE, respectively, did not result in any accumulation of AhR agonist activity after completed digestion, even though chemical analysis indicate a dechlorination of PCBs. Complex, unfractionated extracts were difficult to test using the bioassay approach. Removal of AhR antagonists or otherwise interacting compounds during fractionation may yield bio-TEQ values that are much higher than in the original extract. Recommendations and Perspectives. Our results indicate that the environmental risk that AhR agonists may pose concerning largescale anaerobic digestion of organic household waste probably depends on the efficiency of the digester and the sludge residence time. in order to obtain reliable results with the bioassays, an extensive cleanup and fractionation procedure is necessary. Without clean up and fractionation, there is a risk for false negatives and misleading conclusions. DR-CALUX and CELCAD were both suitable for these kinds of studies, provided that suitable fractionation methods are used.

  • 14.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Schnürer, Anna
    Björnfoth, Helén
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Fractionation and determination of Ah receptor (AhR) agonists in organic waste after anaerobic biodegradation and in batch experiments with PCB and decaBDEManuscript (Other academic)
  • 15.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Björnfoth, Helén
    Örebro University, Department of Natural Sciences.
    Hardell, Lennart
    Lindström, Gunilla
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    CALUX-TEQs, PCDD/F and PCB in SFE-extracts of human adipose tissue from breast cancer patientsManuscript (Other academic)
  • 16.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Kalbin, Georgi
    Örebro University, Department of Natural Sciences.
    Pettersson, Anneli
    Örebro University, Department of Natural Sciences.
    Stenlund, Sara
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Formation of dioxin-like compounds as photoproducts of decarbominated diphenyl ether (deBDE) during UV-irradiation2002In: Organohalogen Compounds, ISSN 1026-4892, Vol. 58, p. 41-44Article in journal (Refereed)
  • 17.
    Olsman [Takner], Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Kammann, Ulrike
    Klempt, Martin
    Otte, Jens
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Hollert, Henner
    Relative differences in aryl hydrocarbon receptor-mediated response for 18 polybrominated and mixed halogenated dibenzo-p-dioxins and -furans in cell lines from four different species2007In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 26, no 11, p. 2448-2454Article in journal (Other academic)
    Abstract [en]

    As a consequence of ubiquitous use of brominated organic chemicals, there is a concern for persistent or increasing environmental levels of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) and mixed polychlorinated and polybrominated dibenzo-p-dioxins/furans (PXDD/Fs). Hence, there is a need to broaden the toxicological and environmental knowledge about these compounds, as a basis for risk assessment. In the study presented here, the relative potencies (REPs) for 18 PBDD/F and PXDD/ F congeners were determined in four dioxin-specific bioassays from different species: dioxin receptor chemically activated luciferase expression assay (DR-CALUX, rat hepatoma cells), TV101L (human hepatoma cells), and GPC.2D (guinea pig adenoma cells), as well as ethoxyresorufin-O-deethylase induction in the fish cell line RTL-W1 (rainbow trout liver cells). The bioassay specific REP factors presented here enable the assessment of the contribution from PBDD/Fs and PXDD/Fs to total 2,3,7,8-tetrachl orodibenzop-dioxin (TCDD) equivalents (TEQs: toxic equivalents), using bioassay analysis. The PBDD/Fs were found to be equally potent as their chlorinated analogues in the three mammalian assays, whereas the PXDD/Fs showed relatively higher potencies. Of special concern were the 2,3,7,8-substituted penta- and tetrahalogenated congeners, for which mean REPs were >= 1. The 2-B-1,3,7,8-CDD (2-bromo-1,3,7,8-tetrachlorodibenzo-p-dioxin) was up to three times more potent than TCDD in individual experiments (on weight basis). The RTL-W1 was less sensitive to the tested compounds with overall 10-fold lower REPs than the mammalian cell lines. Although the REP factors exhibited species-specific differences, overall resembling rank orders of dioxin-like potency were obtained.

  • 18. Otte, Jens C.
    et al.
    Andersson, Carin
    Abrahamson, Alexandra
    Olsman Takner, Helena
    Örebro University, Department of Natural Sciences.
    Keiter, Steffen
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Hollert, Henner
    Brunström, Björn
    A bioassay approach to determine the dioxin-like activity in sediment extracts from the Danube River: ethoxyresorufin-O-deethylase induction in gill filaments and liver of three-spined sticklebacks (Gasterosteus aculeatus L.)2008In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 34, no 8, p. 1176-1184Article in journal (Refereed)
    Abstract [en]

    Sediment samples from the upper Danube River in Germany have previously been characterized as ecotoxicologically hazardous and contaminants in these sediments may contribute to the observed decline of fish populations in this river section. For the investigation of sediment toxicity there is a need for development, standardization and implementation of in vivo test systems using vertebrates. Therefore, the main objective of this study was to apply and evaluate a recently established fish gill EROD assay as a biomarker in sediment toxicity assessment by using extracts of well characterised sediment samples from the upper Danube River. This to our knowledge is the first application of this novel assay to sediment extracts. Sediments from four different sites along the upper Danube River were Soxhlet-extracted with acetone and dissolved in DMSO. Three-spined sticklebacks (Gasterosteus aculeatus L.) were exposed for 48 h to various concentrations of the extracts, to the positive control β-naphthoflavone or to the solvent. Measurements of EROD activity in gill filaments and liver microsomes followed the exposure. Concentration-dependent induction of EROD in both gill and liver was found for all sediment extracts. The highest EROD-inducing potency was determined for extracts of sediments from the sites “Öpfinger See” and “Sigmaringen” and the EROD activities in gill and liver correlated well. The results from the gill and liver assays were in accordance with in vitro results of previous investigations. The EROD activities measured in the present study corresponded with the concentrations of PAHs, PCBs and PCDD/Fs in the sediment samples derived in a previous study. The sticklebacks in this study were in the reproductive phase and a stronger EROD induction was obtained in the females than in the males. Implementation of the EROD assay in testing of sediment extracts gave highly reliable results which make this assay an ecotoxicologically relevant method for assessment of contamination with Ah receptor agonists in sediments.

  • 19. Wölz, Jan
    et al.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Maletz, Sibylle
    Olsman Takner, Helena
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Kammann, Ulrike
    Klempt, Martin
    Weber, Roland
    Braunbeck, Thomas
    Hollert, Henner
    Changes in toxicity and Ah receptor agonist activity of suspended particulate matter during flood events at the rivers Neckar and Rhine - a mass balance approach using in vitro methods and chemical analysis2008In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 15, no 7, p. 536-553Article in journal (Refereed)
    Abstract [en]

    Background, aim, and scope  As a consequence of flood events, runoff and remobilized sediments may cause an increase of ecotoxicologically relevant effects from contaminant reservoirs. Aquatic and terrestrial organisms as well as cattle and areas of settlement are exposed to dislocated contaminants during and after flood events. In this study, the impacts of two flood events triggered by intense rain at the rivers Neckar and Rhine (Southern Germany) were studied. Effects in correlation to flood flow were assessed at the river Neckar using samples collected at frequent intervals. River Rhine suspended particulate matter (SPM) was sampled over a longer period at normal flow and during a flood event. Three cell lines (H4L1.1c4, GPC.2D.Luc, RTL-W1) were used to compare Ah receptor agonist activity in different biotest systems. Multilayer fractionation was performed to identify causative compounds, focusing on persistent organic contaminants. Materials and methods  Native water and SPM of flood events were collected at the river Neckar and at the monitoring station (Rheinguetestation, Worms, Germany) of the river Rhine. Water samples were XAD-extracted. SPM were freeze-dried and Soxhlet-extracted using acetone and finally dissolved in dimethyl sulfoxide. Resulting crude extracts were analyzed for cytotoxicity with the neutral red assay. Aryl hydrocarbon receptor (AhR) agonist activity was measured in a set of biological test systems (DR-CALUX, GPC.2D, and ethoxyresorufin-O-deethylase (EROD) assay) and different cell lines. In addition, crude extracts were fractionated using a combined method of multilayer (sequence of acidified silica layers) and carbon fractionation. Fractions from the multilayer fractionation contained persistent organic compounds (polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and some polycyclic aromatic hydrocarbon (PAHs)); fractions from the carbon fractionation were separated into a PCDD/F and a PCB fraction. Dioxin-like activity of multilayer and carbon fractions was determined in the EROD assay and expressed as biological toxicity equivalency concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (bio-TEQs). The calculation of chemical equivalency concentrations (chem-TEQs) and comparison to bio-TEQ values allowed the determination of the contribution of the analyzed persistent compounds to the total biological effects measured. Results  Soluble compounds in native and extracted water samples resulted in no or minor activity in the toxicity tests, respectively. Filter residues of native water caused increased AhR-mediated activity at the peak of the flood. Activities of SPM of the river Neckar correlated well with the flow rate indicating a flood-dependent increase of toxicity culminating at the peak of flow. River Rhine SPM showed a decrease of activity regarding an SPM sample of the flood event compared to a long-term sample. Excellent correlations with AhR agonistic activity were determined for DR-CALUX and EROD assay, while the GPC.2D assay did not correlate with both other biotests. The activity of persistent dioxin-like acting compounds in multilayer and carbon fractionated PCDD/F and PCB fractions was low if compared to corresponding crude extracts. The congener pattern of PCDD/F revealed that the contaminations mainly originated from products and productions of the chlorine and organochlorine industries. Discussion  Native and extracted water samples could be shown to contain little or no cytotoxic or AhR agonistic compounds. In contrast, particle-bound compounds were shown to be the relevant effect-causing fraction, as indicated by the activities of filter residues of native water and SPM. Compounds other than fractionated persistent PCBs and PCDD/Fs were more relevant to explain AhR-mediated activities of crude flood SPM at both rivers assessed. Biologically detected activities could at least in part be traced back to chemically analyzed and quantified compounds. Conclusions  The calculation of the portion of persistent PCBs and PCDD/Fs in multilayer fractions causing the high inductions in the EROD assay in combination with chemical analysis provides a suitable tool to assess dioxin-like activity of persistent compounds in SPM sampled over the course of flood events. Depending on the catchment area and annual course of flood events, end points may either indicate an increase or a decrease of activity. In order to determine the ecological hazard potential of mobilized contaminants during flood events, the focus should be set on particle-bound pollutants. Furthermore, PCDD/Fs and PCBs, commonly expected to be the most relevant pollutants in river systems, could be shown to contribute only to a minor portion of the overall AhR-mediated activity. However, they might be most relevant for human exposure when considering persistence and bioaccumulation–biomagnification in the food chain. Recommendations and perspectives  As a consequence of climate change, flood events will increase in frequency and intensity at least in some regions such as Central Europe. Thus, it is crucial to identify the potential hazard of (re-)mobilized contaminants from reservoirs dislocated via floods and threatening especially aquatic organisms and cattle grazing in flood plains. Since other less persistent compounds seem to be more relevant to explain AhR-mediated activities in flood SPM, nonconventional PAHs and more polar compounds also need to be considered for risk assessment. Effect-directed analysis using broad-range fractionation methods taking into account compounds from polar to nonpolar should be applied for identification of pollutants causing biological effects, thus integrating biological and chemical parameters.

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