| 1. |
- Danielsson, Conny, et al.
(författare)
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Comparison of Levels of PCDD/Fs and non-Ortho PCBs in PCB 153 from seven different suppliers
- 2008
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Ingår i: Organohalogen Compounds. ; 70, s. 001201-3
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Tidskriftsartikel (refereegranskat)abstract
- Twelve PCBs with dioxin-like (DL) properties have been carefully studied through the years to facilitate risk assessment and they have been assigned WHO-TEF values [1] based on their relative toxicity and endocrine effects compared to 2,3,7,8-TCDD. From a toxicological point of view, the non-dioxin-like PCBs (NDL-PCBs) are less characterized but usually account for more than 90% of the total mass of PCBs in food samples [2]. Furthermore, over 90% of the NDL-PCB exposure in the general population is via food and the average daily intake can be estimated to be 10-45 ng/kg (bw)/day according to the European Food Safety Authority EFSA [3]. The EFSA committee concluded that a proper risk assessment of this abundant and environmentally significant class of compounds could not be accomplished. In 2006, the European Commission initiated a project which has as its aim to better examine the toxicity of NDL-PCBs: ATHON- "Assessing the toxicity and hazard of nondioxin-like PCBs present in food". The ATHON project will perform all in vivo and in vitro studies with ultra pure PCBs with known levels of DL-PCBs, PCDD/Fs and total TEQ-levels. As a first step in this study the major suppliers of PCB 153 were identified and the aim of the research was to investigate if there were any clear differences in the quality of their products based on possible impurities of PCDD/Fs and non-ortho PCBs. PCB 153 was selected because of its relatively high presence in environmental compartments and biota and since it has been the most frequently studied NDL-PCB in a few major in vivo studies [2]. Impurities of PCDD/Fs and DL-PCBs, even at trace levels, in PCB 153 may make a significant contribution to the effects seen in in vivo studies as the highest concentrations being studied are at mg/g (bw)/day during a period of time. These high daily exposure levels in combination with possible accumulation of toxic impurities may by time pose a threat to the significance of observed effects. Within the ATHON project all NDL-PCBs used for both in vitro and in vivo tests are analyzed and in many cases purified to remove possible traces of PCDD/Fs and non-ortho PCBs.
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| 2. |
- Harju, Mikael, et al.
(författare)
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Quantitative Structure–Activity Relationship Modeling on in Vitro Endocrine Effects and Metabolic Stability Involving 26 Selected Brominated Flame Retardants
- 2007
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Ingår i: Environmental Toxicology and Chemistry. - 1552-8618. ; 26:4, s. 816-26
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Tidskriftsartikel (refereegranskat)abstract
- In this work, quantitative structure–activity relationships (QSARs) were developed to aid human and environmental risk assessment processes for brominated flame retardants (BFRs). Brominated flame retardants, such as the high-production-volume chemicals polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A, and hexabromocyclododecane, have been identified as potential endocrine disruptors. Quantitative structure–activity relationship models were built based on the in vitro potencies of 26 selected BFRs. The in vitro assays included interactions with, for example, androgen, progesterone, estrogen, and dioxin (aryl hydrocarbon) receptor, plus competition with thyroxine for its plasma carrier protein (transthyretin), inhibition of estradiol sulfation via sulfotransferase, and finally, rate of metabolization. The QSAR modeling, a number of physicochemical parameters were calculated describing the electronic, lipophilic, and structural characteristics of the molecules. These include frontier molecular orbitals, molecular charges, polarities, log octanol/water partitioning coefficient, and two- and three-dimensional molecular properties. Experimental properties were included and measured for PBDEs, such as their individual ultraviolet spectra (200–320 nm) and retention times on three different high-performance liquid chromatography columns and one nonpolar gas chromatography column. Quantitative structure–activity relationship models based on androgen antagonism and metabolic degradation rates generally gave similar results, suggesting that lower-brominated PBDEs with bromine substitutions in ortho positions and bromine-free meta- and para positions had the highest potencies and metabolic degradation rates. Predictions made for the constituents of the technical flame retardant Bromkal 70-5DE found BDE 17 to be a potent androgen antagonist and BDE 66, which is a relevant PBDE in environmental samples, to be only a weak antagonist.
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| 3. |
- Heimstad, Eldbjørg Sofie, et al.
(författare)
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Quantitative structure-Photodegradation relationships of polybrominated diphenyl ethers, phenoxyphenols and selected organochlorines
- 2009
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 77:7, s. 914-921
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Tidskriftsartikel (refereegranskat)abstract
- Among other developments, the technological revolution has lead to introduction of new chemicals to better serve in instruments and materials. The consequences of the extensive increase in use of new chemicals can be detected in the environment world wide, i.e. in wildlife and humans. To ensure this problem to be minimised in the future, new chemicals need to be subjected to predictive assessments before commercialised. To facilitate screening, qualitative structure-activity relationships, quantitative structure-activity relationships may be applied to describe reactivity of chemicals. Physico-chemical properties of chemicals such as partition coefficients and half-lives for the various environmental compartments are essential input data in multimedia environmental fate models. In this study we examine how structural characteristics can quantitatively describe laboratory determined photolytic half-lives of halogenated compounds of different classes, such as polybrominated diphenyl ethers (PBDEs), hydroxylated brominated diphenyl ethers (OH-PBDEs), and other organohalogens. A total of 30 chemicals with experimentally measured half-lives are used. Results reveal that the most important descriptors for describing the half-lives of the brominated compounds are the energy gap (GAP-1) between HOMO-1 and LUMO, the lowest partial charge on a halogen atom (Qhal-), topological polar surface area (TPSA), the atom with highest radical superdelocalizability (Rad-super+) and LUMO density (LUMO+).
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