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| 2. |
- Bergknut, Magnus, et al.
(författare)
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Identification of potentially toxic compounds in complex extracts of environmental samples using gas chromatography-mass spectrometry and multivariate data analysis
- 2007
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Ingår i: Environmental Toxicology and Chemistry. - New York : Pergamon. - 0730-7268 .- 1552-8618. ; 26:2, s. 208-217
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we examined 31 samples of varying chemical composition, including samples of soils from gasworks, coke production sites, and sites where wood preservatives were heavily used; ash and soot from municipal solid waste incinerators; antiskid sand; and dust from areas with heavy road traffic. The samples were comprehensively chemically characterized, especially their polycyclic aromatic compound contents, using gas chromatography-time-of-flight mass spectrometry, whereas their biological effects were assessed using dehydrogenase activity, root growth (Hordeum vulgare), reproduction of springtails (Folsomia candida), algal growth (Desmodesmus subspicatus), germinability (Sinapis alba), Vibrio fischeri, DR-CALUX, and Ames Salmonella assays. The number of compounds detected in the samples ranged from 123 to 527. Using the multivariate regression technique of partial-least-squares projections to latent structures, it was possible to find individual compounds that exhibited strong correlations with the different biological responses. Some of the results, however, indicate that a broader chemical characterization may be needed to identify all the compounds that may cause the measured biological responses.
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| 3. |
- Hollert, Henner, et al.
(författare)
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Biological and Chemical Determination of Dioxin-like Compounds in Sediments by Means of a Sediment Triad Approach in the Catchment Area of the River Neckar
- 2002
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Ingår i: Ecotoxicology. - 0963-9292 .- 1573-3017. ; 11:5, s. 323-36
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Jonsson, Sofia, 1973-, et al.
(författare)
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Degradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils by Fenton's reagent : a multivariate evaluation of the importance of soil characteristics and PAH properties
- 2007
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 149:1, s. 86-96
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated how the chemical degradability of polycyclic aromatic hydrocarbons (PAHs) in aged soil samples from various contaminated sites is influenced by soil characteristics and by PAH physico-chemical properties. The results were evaluated using the multivariate statistical tool, partial least squares projections to latent structures (PLS). The PAH-contaminated soil samples were characterised (by pH, conductivity, organic matter content, oxide content, particle size, specific surface area, and the time elapsed since the contamination events, i.e. age), and subjected to relatively mild, slurry-phase Fenton's reaction conditions. In general, low molecular weight PAHs were degraded to a greater extent than large, highly hydrophobic variants. Anthracene, benzo(a)pyrene, and pyrene were more susceptible to degradation than other, structurally similar, PAHs; an effect attributed to the known susceptibility of these compounds to reactions with hydroxyl radicals. The presence of organic matter and the specific surface area of the soil were clearly negatively correlated with the degradation of bi- and tri-cyclic PAHs, whereas the amount of degraded organic matter correlated positively with the degradation of PAHs with five or six fused rings. This was explained by enhanced availability of the larger PAHs, which were released from the organic matter as it degraded. Our study shows that sorption of PAHs is influenced by a combination of soil characteristics and physico-chemical properties of individual PAHs. Multivariate statistical tools have great potential for assessing the relative importance of these parameters.
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| 5. |
- Olsman, Helena, et al.
(författare)
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Ah receptor agonists in UV-exposed toluene solutions of decabromodiphenyl ether (decaBDE) and in soils contaminated with polybrominated diphenyl ethers (PBDEs)
- 2006
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Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 13:3, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- van den Berg, Martin, et al.
(författare)
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Polybrominated Dibenzo-p-Dioxins, Dibenzofurans, and Biphenyls : Inclusion in the Toxicity Equivalency Factor Concept for Dioxin-Like Compounds
- 2013
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Ingår i: Toxicological Sciences. - Oxfors, United Kingdom : Oxford University Press. - 1096-6080 .- 1096-0929. ; 133:2, s. 197-208
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Forskningsöversikt (refereegranskat)abstract
- In 2011 a joint World Health Organization (WHO) and United Nations Environment Programme (UNEP) expert consultation took place, during which the possible inclusion of brominated analogues of the dioxin-like compounds in the WHO Toxicity Equivalency Factor (TEF) scheme were evaluated. The expert panel concluded that polybrominated dibenzo-p-dioxins (PBDDs), dibenzofurans (PBDFs), and some dioxin-like biphenyls (dl-PBBs) may contribute significantly in daily human background exposure to the total dioxin toxic equivalencies (TEQs). These compounds are also commonly found in the aquatic environment. Available data for fish toxicity were evaluated for possible inclusion in the WHO-UNEP TEF scheme (Van den Berg et al., 1998). Because of the limited database it was decided not to derive specific WHO-UNEP TEFs for fish, but for ecotoxicological risk assessment the use of specific relative effect potencies (REPs) from fish embryo assays is recommended. Based on the limited mammalian REP database for these brominated compounds, it was concluded that sufficient differentiation from the present TEF values of the chlorinated analogues (Van den Berg et al., 2005) was not possible. However, the REPs for PBDDs, PBDFs, and non-ortho dl-PBBs in mammals closely follow those of the chlorinated analogues, at least within one order of magnitude. Therefore, the use of similar interim TEF values for brominated and chlorinated congeners for human risk assessment is recommended, pending more detailed information in the future.
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| 7. |
- Van den Berg, Martin, et al.
(författare)
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The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds
- 2006
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Ingår i: Toxicological Sciences. - : Oxford University Press. - 1096-6080 .- 1096-0929. ; 93:2, s. 223-241
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Tidskriftsartikel (refereegranskat)abstract
- In June 2005, a World Health Organization (WHO)-International Programme on Chemical Safety expert meeting was held in Geneva during which the toxic equivalency factors (TEFs) for dioxin-like compounds, including some polychlorinated biphenyls (PCBs), were reevaluated. For this reevaluation process, the refined TEF database recently published by Haws et al. (2006, Toxicol. Sci. 89, 4-30) was used as a starting point. Decisions about a TEF value were made based on a combination of unweighted relative effect potency (REP) distributions from this database, expert judgment, and point estimates. Previous TEFs were assigned in increments of 0.01, 0.05, 0.1, etc., but for this reevaluation, it was decided to use half order of magnitude increments on a logarithmic scale of 0.03, 0.1, 0.3, etc. Changes were decided by the expert panel for 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) (TEF = 0.3), 1,2,3,7,8-pentachlorodibenzofuran (PeCDF) (TEF = 0.03), octachlorodibenzo-p-dioxin and octachlorodibenzofuran (TEFs = 0.0003), 3,4,4',5-tetrachlorbiphenyl (PCB 81) (TEF = 0.0003), 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169) (TEF = 0.03), and a single TEF value (0.00003) for all relevant mono-ortho-substituted PCBs. Additivity, an important prerequisite of the TEF concept was again confirmed by results from recent in vivo mixture studies. Some experimental evidence shows that non-dioxin-like aryl hydrocarbon receptor agonists/antagonists are able to impact the overall toxic potency of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds, and this needs to be investigated further. Certain individual and groups of compounds were identified for possible future inclusion in the TEF concept, including 3,4,4'-TCB (PCB 37), polybrominated dibenzo-p-dioxins and dibenzofurans, mixed polyhalogenated dibenzo-p-dioxins and dibenzofurans, polyhalogenated naphthalenes, and polybrominated biphenyls. Concern was expressed about direct application of the TEF/total toxic equivalency (TEQ) approach to abiotic matrices, such as soil, sediment, etc., for direct application in human risk assessment. This is problematic as the present TEF scheme and TEQ methodology are primarily intended for estimating exposure and risks via oral ingestion (e.g., by dietary intake). A number of future approaches to determine alternative or additional TEFs were also identified. These included the use of a probabilistic methodology to determine TEFs that better describe the associated levels of uncertainty and "systemic" TEFs for blood and adipose tissue and TEQ for body burden.
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