Polychlorinated dibenzofurans degradation

Takada S, M Nakamura, T Matsueda, R Kondo, K Sakai (1996) Degradation of polychlorinated dibenzo-/ -dioxins and polychlorinated dibenzofurans by the white rot fnngns Phanerochaete sordida YK-624. Appl Environ Microbiol 62 4323-4328. 

Vollmuth, S. and Niessner R., Degradation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans during the UV/ozone treatment of pentachlo-rophenol-containing water, Toxicol. Environ. Chem., 61, 27-41, 1997. 

Choudhary, G.G., Hutzinger, O. (1982) Photochemical formation and degradation of polychlorinated dibenzofurans and dibenzo-p-dioxins. Residue Rev. 84, 113-161. 

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) have attracted considerable attention in recent decades, owing to concern over their potential adverse effects in humans and wildlife, which are compounded by their ubiquitous environmental presence and resistance to degradation. Amongst the 75 possible PCDDs, 135 PCDFs and 209 PCBs, there exists wide variation in physicochemical properties, bioaccumulative tendencies and toxicity. Figures 1 and 2 illustrate the basic structures and nomenclature of both PCDDs, PCDFs collectively referred to as PCDD/Fs-and PCBs. 

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorobiphenyls (PCBs), and polychlorophenols (PCPs) are well-known artifacts ubiquitous in the present environment. Due to their lipophilic-ity and resistance to metabolism or chemical degradation these have the potential to accumulate in the food chain and cause toxic effects [1, 2]. Polycyclic aromatic sulfur heterocycles (PASHs) along with different kinds of polycyclic aromatic compounds (PACs) also occur widely in the environment [3,4]. In particular, alkylated dibenzothiophenes have previously been found to be persistent residues in the marine environment after oil spills. Dibenzothiophene and its alkylated derivatives have been found to accumulate in fish and other marine organisms [5-7]. 

The CDP-Process works well on several stable, halogenated aromatic derivatives mainly studied, also in connection with its industrial application has been the PCB and the degradation products that PCB forms as a consequence of fire that is polychlorinated dibenzofurans and dioxins (PCDF and PCDD, respectively). 

Pathways and biocatalysts of bacterial degradation quinolines 98AG(E)577. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in marine products and estimation of exposure through fishes and shellfishes 97 YZ850. Stereocontrolled synthesis of multifunctional bioactive 7-10-member O-hetero-cycles 97YGK44. 

Koester CJ, Hites RA. 1992. Photo degradation of polychlorinated dioxins and dibenzofurans adsorbed to fly ash. Environ Sci Technol 26(3) 502-507. 

Pignatello JJ, Huang FQ. Degradation of polychlorinated dibenzo-/>-dioxin and dibenzofuran contaminants in 2,4,5-T by photoassisted iron-catalyzed hydrogen peroxide. Water Res 1993 27 1731-1736. 

Polychlorinated diphenyl ethers (PCDE) are common impurities in chlorophenol formulations, which were earlier used as fungicides, slimicides, and as wood preservatives. PCDEs are structurally and by physical properties similar to polychlorinated biphenyls (PCB). They have low water solubility and are lipophilic. PCDEs are quite resistant to degradation and are persistent in the environment. In the aquatic environment, PCDEs bioaccumulate. These compounds are found in sediment, mussel, fish, bird, and seal. PCDEs show biomagnification potential, since levels of PCDEs increase in species at higher trophic levels. PCDEs are also detected in human tissue. Despite the persistence and bio accumulation, the significance of PCDEs as environmental contaminants is uncertain. The acute toxicity and Ah-receptor-me-diated (aryl hydrocarbon) activity of PCDEs is low compared to those of polychlorinated di-benzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Due to structural similarity to thyroid hormone, PCDEs could bind to thyroid hormone receptor and alter thyroid function. Furthermore, PCDEs might be metabolized to toxic metabolites. In the environment, it is possible that photolysis converts PCDEs to toxic PCDDs and PCDFs. 

The principal direction of the published photochemical research to date has been to elucidate pathways which might be responsible for the degradation of these refractory substances in nature. This basic research has not been extensively applied either to on-or off site treatment of hazardous substances. In this chapter we extend the existing PCB photochemistry literature by considering this potential. The development and fabrication of a prototype surface photoreactor, and its preliminary evaluation at a PCB-contaminated site are described. Photochemical treatments may be applicable to many other classes of hazardous chemicals as well including the polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF) about which this monograph is chiefly concerned. 

Persistent or non-degradable environmental chemicals - even those with low volatility - may be dispersed around the globe. Polychlorinated biphenyls (PCB), polychlorinated dibenzodioxins and dibenzofurans (PCDD, PCDF), l,l,l-trichlor-2,2-bis(4-chlorphenyl)-ethan DDT, hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB) have been found in samples from the Arctic and Antarctic and in the tissues of marine animals. Although the open use of many of these chemicals has been prohibited in most industrialized countries, considerable residues still remain in the environment. It is estimated that about 20% of the global production of PCBs (230 000 t/a) persists in the upper layers of the oceans and that a further 7901 are present in the atmosphere (Fiedler and Lau, 1998). Such contamination may accumulate in organisms and have negative effects that go as far as the death of whole populations in ecosystems (Jdrgensen, 1998). 

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