| 21. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Dioxins : Sources of environmental load and human exposure
- 1990
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Ingår i: Toxicological & Environmental Chemistry. - : Taylor & Francis. - 0277-2248 .- 1029-0486. ; 29:3, s. 157-234
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated dibenzo‐p‐dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) represent a class of tricylic, almost planar, aromatic ethers with 1 to 8 chlorine atoms. Congeners with substituents in the positions 2, 3, 7, and 8 are of special concern due to their toxicity, stability, and persistence. These compounds have been identified in almost all environmental compartments and humans.Dioxins are a potent carcinogen for animals and—at the moment—considered a probable carcinogen for humans. Actual toxicological risk assessment for humans are based on 2,3,7,8‐Cl4DD carcinogenicity studies on rodents. Tumorigenic effects were found for 2 strains of rats and 2 strains of mice. All dioxins and furans elicit common toxic and biological responses, starting with a specific binding to a protein receptor, but existing epidemiologic data do not provide definitive data on human health effects.Toxicity equivalency factors (TEFs) have been developed by several agencies as a provisional method of risk assessment for complex mixtures of PCDD/PCDF.Dioxins have never been produced intentionally and have never served any useful purpose. They are formed in trace amounts as by‐products in industrial processes; for instance within the chemical industry, of the pulp and paper industry, metallurgical processes, processes for reactivation of granular carbon, dry cleaning, and the manufacture of flame‐retarded plastics.The main pathway for dioxins to enter the environment is via combustion processes. Incineration is of special importance since PCDD/PCDF are directly released to the atmosphere from either stationary sources, such as municipal, hazardous and hospital waste incinerators, the combustion of sewage sludge, and scrap metal recycling, or diffuse sources, e.g. automobile exhausts, private home heating with fossil fuels, forest fires, and cigarette smoking. Furthermore, fires with PCB and PVC have additionally contributed to the total dioxin load. The emission gases can undergo long‐range transport, so that dioxins have been found even in remote areas.Besides the two primary sources (industrial processes and combustion processes) the release of dioxins from contaminated areas and waste dumps via the leachate and the application of sewage sludge for fertilization represents a third source of PCDD/PCDF.After more than 10 years of dioxin research the most important sources of PCDD/PCDF have been identified and analytical methods have been developed for their quantification in trace levels and in complex matrices.Various efforts have been undertaken to reduce the emission of dioxins: for example, optimization of combustion processes for municipal waste incineration, use of unleaded gasoline, ban of chemicals, such as polychlorinated biphenyls (PCBs) and pentachlorophenol (PCP). More detail is provided in the pulp and paper section where changes have been initiated to significantly reduce the sources of PCDD/PCDF.However, relatively little is known about transport and transformation processes, so only rough estimates can be made. Photodegradation has been found to be the primary process for 2,3,7,8‐Cl4DD breakdown. A half‐life of 3–4 days has been estimated for photochemical degradation under oxidative conditions. Field studies on the fate of 2,3,7,8‐Cl4DD in soil gave a half‐life of 9.1 (Seveso) and 12 years (under special conditions: sand, erosion), respectively. Biodegradation seems to be negligible. Transfer factors soil‐plants for PCDD/PCDF have been determined—with a high degree of uncertainty—to be less than 0.1.Human exposure primarily occurs via ingestion whereas inhalation is a minor pathway. Dermal absorption can be neglected although skin contact to polluted surfaces may occur. Due to the lipophilicity of PCDD/PCDF and their potential for accumulation, foods such as meat and especially dairy products contribute most to the dioxin body burden of humans.Both national agencies and international organizations have recognized the significance of this problem and as a result have initiated regulations, recommendations and research programmes (1) to understand where and how PCDD/PCDF are formed, (2) to reduce their impact on the environment and to humans, and (3) to start remedial action on contaminated areas.
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| 22. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Patterns and sources of polychlorinated dibenzo-p-dioxins and dibenzofurans found in soil and sediment samples in southern Mississippi
- 1996
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 32:3, s. 421-432
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Tidskriftsartikel (refereegranskat)abstract
- Using hierarchical cluster analysis and Principal Component Analysis (PCA), sediment and soil samples from the State of Mississippi were compared with the effluents of a pulp mill, a potential point source. Additionally, data of many known sources of PCDD/PCDF from the scientific literature were evaluated. Both methods were able to distinguish between different matrices with known PCDD/PCDF contamination (e.g. PCP, PCB, kraft pulp mill effluents). In some instances, a specific PCDD/PCDF source could be correlated to an environmental sample, e.g. the pattern of a U.S, brand of pentachlorophenate was found in sediment samples. None of the mathematical and statistical techniques could identify the pulp mill as the source of the PCDD/PCDF in the sediments and soils in the floodplain.
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| 23. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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PCDD, PCDF, and PCB in farm-raised catfish from southeast United States - Concentrations, sources, and CYP1A induction
- 1998
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 37:9-12, s. 1645-1656
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Tidskriftsartikel (refereegranskat)abstract
- Nine catfish fillets, three catfish nuggets, two feed samples, and one pond sediment were analyzed for PCDD, PCDF, and-PCB. Farm-raised catfish from Mississippi, Alabama, and Arkansas contained significant levels of 2,3,7,8-substituted PCDD and PCDF. In addition, a large number of non-2,3,7,8-substituted congeners were present in all samples. The catfish fillets and catfish nuggets also contained high concentrations of dioxin-like PCB, as well as a number of non-dioxin-like PCB. The TEQ based on PCDD and PCDF ranged from 9.5 to 43.0 pg/g lipid and the TEQ based on PCB ranged from 0.45 to 4.9 pg/g lipid for all catfish samples. The dioxin-like PCB contributed 4-16% to the total TEQ (PCDD/PCDF/PCB) for the catfish samples. The major source for the PCDD, PCDF, and PCB appears to be from feed and not from pond sediment. Immunoreactive CYP1A protein was elevated 2.5 fold in the pond-raised catfish compared to the aquarium-raised one. The results of this study suggest that the PCDD/PCDF are more important than the PCB in the CYP1A induction.
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| 24. |
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| 25. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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QSAR generated octanol-water partition coefficients of selected mixed halogenated dibenzodioxins and dibenzofurans
- 1990
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 20:10-12, s. 1597-1602
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Tidskriftsartikel (refereegranskat)abstract
- We have calculated the values of pkow, water solubility, and Koc for chlorinated, brominated and mixed halogenated dibenzodioxins and dibenzofurans that have been identified in environmental samples. From the results it can be concluded that brominated and mixed halogenated dioxins and furans will show an ecological behaviour similar to that of the pure chlorinated compounds.
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| 26. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Sources and sinks of dioxins : Germany
- 1992
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 25:7-10, s. 1487-1491
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Tidskriftsartikel (refereegranskat)abstract
- Combustion processes are known to produce dioxins and especially municipal waste incineration is thought to have the highest contribution to the general background. On the other hand the general acceptance of non-thermal waste treatment methods such as composting is much higher than incineration. The results of an estimation on the input of PCDD/PCDF to Germany show that besides the thermal processes so-called sinks for pollutants, such as sewage sludge, compost, and foliage represent a reservoir to release dioxins by use in agriculture.
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| 27. |
- Fiedler, Heidelore, 1953-
(författare)
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Sources of PCDD/PCDF and impact on the environment
- 1996
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 32:1, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- PCDD/PCDF can be formed in a variety of industrial and thermal processes. Especially the combustion sources contribute to the ambient air levels. In addition to the well-investigated emissions from municipal waste incinerators dioxins were measured in the flue gases of other thermal emitters. It was found that some recycling plants can emit high concentrations of PCDD/PCDF. Ambient air concentrations monitored over several years have shown a clear seasonal trend with higher PCDD/PCDF levels in winter and lower concentrations during summer. Thus, results from short-term measurements cannot be used to calculate annual means for ambient air concentations or deposition rates. Dioxins, once concentrated in sewage sludge and compost can re-enter the environment when these ''reservoirs'' are applied onto agricultural and horticultural soils.
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| 28. |
- Fiedler, Heidelore, 1953-
(författare)
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Thermal formation of PCDD/PCDF : A survey
- 1998
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Ingår i: Environmental Engineering Science. - : Mary Ann Liebert. - 1092-8758 .- 1557-9018. ; 15:1, s. 49-58
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Tidskriftsartikel (refereegranskat)abstract
- Since polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) were quantified in the emissions from the Amsterdam municipal solid waste incinerator (MSWI) in 1977, more than 20 years of intensive research gave many answers on how PCDD and PCDF can form in thermal processes. As a result, it can be concluded that PCDD/PCDF can be formed in all combustion processes where organic carbon, oxygen, and chlorine are present. Although there are still open questions, findings can be summarized as follows:PCDD/PCDF can be formed in the gas phase as well as in the heterogeneous phase.Geometry of the combustion chamber, time, temperature, feeding rate, input (chlorine), and so forth may have an influence on the formation of PCDD/PCDF.There may be different processes dominating to form PCDD or PCDF.The amount of PCDD and PCDF formed differs between types of thermal processes.Within the same process categories, e.g., MSWIs, hazardous waste incinerators, steel mills, etc., the PCDD/PCDF pattern is very similar.Formation of PCDD/PCDF can be prevented by addition of "inhibitors" such as sulfur- or nitrogen-containing agents.Results from field investigations, i.e., waste wood combustion and a new technology for thermal treatment of municipal solid waste, support these basic findings.
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| 29. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Utility of the QSAR modeling system for predicting the toxicity of substances on the European inventory of existing commercial chemicals
- 1990
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Ingår i: Toxicological & Environmental Chemistry. - : Gordon and Breach Publishers. - 0277-2248 .- 1029-0486. ; 28:2-3, s. 167-188
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Tidskriftsartikel (refereegranskat)abstract
- Many chemicals are in common commercial use for which no information on the environmental fate or toxicity exists. Recent legislation requires that many substances be assessed for their toxicity to aquatic organisms within a very short time and determine which of these chemicals need to be studied in greater detail. It would be impossible to measure the acute and chronic effects of all of these compounds on a single organism, let alone a battery of different types of organisms, communities or ecosystems. Initially, the chemicals on the European Inventory of Existing Commercial Chemical Substances (EINECS) need to be screened and relative hazard to the environment determined. In response to OECD directives, there has been a great deal of activity by government and industry scientists. At the International Workshop on Advances in Environmental Hazard and Risk Assessment it was concluded that quantitative structure activity relationships (QSAR) could and should be used in the hazard assessment process. Papers published in that volume outline the advantages, disadvantages, limitations, advances and research requirements.The QSAR, structure‐activity based chemical modeling and information system, which was developed by the US‐Environmental Protection Agency was used to predict the acute toxicity of 113 substances from the “Old Substances”; list of the German government to the four commonly used aquatic toxicity test organisms: Daphnia magna (DM), fathead minnow (FHM), rainbow trout (RBT), and blue‐gill sunfish (BG).Of these compounds the QSAR system predicted the acute toxicity of 87 substances towards fathead minnow. For the other three species examined the QSAR system could be used to predict toxicity for 78 compounds.The predicted toxicities were compared to observed toxicities of compounds which have been evaluated and stored in the “Aquire”; data base. Observed toxicity values were available for at least one species for 38 compounds. The toxicities of some compounds are well predicted while those of other compounds were not well predicted. Overall, the QSAR system accurately classified the acute toxicity ranges of 50%, 64%, 56% and 56% of the compounds investigated for DM, FHM, RBT and BG, respectively. Of the compounds studied 10 were very poorly predicted, of these the QSAR system overpredicted the toxicity of three, while underpredicting the toxicity of seven. Of these seven compounds, five contained amino groups.
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| 30. |
- Hauk, A., et al.
(författare)
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Reduction of nitrated phenols : A method to predict half-wave-potentials of nitrated phenols with molecular modeling
- 1990
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 20:6, s. 717-728
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Tidskriftsartikel (refereegranskat)abstract
- The redox stability of 13 nitrated phenols was investigated using polarographic measured half-wave-potentials. These half-wave-potentials were compared with data from a semi-empirical quantum mechanic computer model. A good correlation was found between LUMO energy and the half-wave-potential for phenols, but for phenolates the correlation coefficient was lower, even when a multivariate regression model was used.
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