Polychlorinated dibenzodioxins PCDDs and dibenzofurans PCDFs

The dioxins, especially 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are extremely toxic and exert effects at submicrogram levels. They are also very lipophilic and persistent and bioaccumulate and biomagnify very effectively. Toxic action is 

Dioxins and other substances (e.g. planar PCB congeners) with affinity for the Ah-receptor give rise to additive toxicity in proportion to the degree of affinity and action on the receptor. Thus, the different congeners are characterized by an affinity factor, the toxic equivalent factor (TEF), which, by multiplication with the actual concentration, gives the toxicity equivalent (TEQ) for the substance. In this context, the TEF of TCDD is set to unity and other substances have TEF 1. By summing up the contributions or TEQs for all the congeners of PCDDs, PCDFs, PCBs, etc. involved, the total toxic impact on the Ah-receptor can be quantified (Paasivirta, 1991). 

Certain PCDDs and PCDFs act as very powerful inducers of the MFO system and give rise to de novo synthesis of CYP1A1, a cytochrome P450 isozyme associated with aryl hydrocarbon hydrolase (AHH or Ah), and ethoxyresorufin O-deethylase (EROD), a common biomarker for PCDD exposure. 

The PCDDs/ PCDFs are highly dangerous envirotoxicants and actions for remediation and for decreasing de novo production of the substances are important, e.g. proper combustion methods and care in handling of chlorinated waste, as well as properly controlled manufacturing and use of chlorine-containing products. 

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Abstract Polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (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. 

Mader, B.T., Pankow, J.F. (2003) Vapor pressures of the polychlorinated dibenzodioxins (PCDDs) and the polychlorinated dibenzofurans (PCDFs). Atmos. Environ. 37, 3103-3114. 

Polychlorinated Dibenzodioxins (PCDDs) and Polychlorinated Dibenzofurans (PCDFs) by High-Resolution GC/High-Resolution MS 8310 Polynuclear Aromatic Hydrocarbons... 

Technical CP formulations contain impurities such as polychlorinated phenoxyphenols (PCPPs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) (Humppi et al., 1984 Kitunen et al., 1985 Jackson Bisson, 1990). Therefore, PCPPs, PCDFs, and PCDDs are often found in CP-contaminated wood treatment sites (Kitunen et al., 1985, 1987 Jackson Bisson, 1990 Kitunen Salkinoja-Salonen, 1990 Trudell et al., 1994). PCPP concentrations up to 78 mg/kg, PCDF up to 3-8 mg/kg, and PCDDs at 13 mg/kg have been detected in CP-contaminated sites (Kitunen et al., 1987 Jackson Bisson, 1990). 

The presence of elevated concentrations of POPs, for example, dioxins [polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran (PCDF)] and PCBs... 

VDI 4300, Part 2 (1997) Indoor air pollution measurement. Measurement strategy for polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzodioxins (PCDDs) and polychlorinated biphenyls (PCBs) in indoor air. Beuth, Berlin. 

I. Mechanism of toxicity. PCBs are irritating to mucous membranes. When burned, PCBs may produce the more highly toxic polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs see p 184). It is difficult to establish the specific effects of PCB intoxication because PCBs are neatly always contaminated with small amounts of these compounds. PCBs, and particularly the PCDD and PCDF contaminants, are mutagenic and teratogenic and are considered potential human carcinogens. 

Polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), often termed dioxins , consist of 210 different compounds which have similar chemical properties. This class of compounds is persistent, toxic, and bioaccumulative. They are generated as byproducts during incomplete combustion of chlorine containing wastes like municipal solid waste, sewage sludge, and hospital and hazardous wastes. Industrial processes such as bleaching of wood pulp in the manufacture of paper products, can also produce PCDDs and PCDFs [39]. 

In addition to the thermogravimetry experiments, batch pyrolysis experiments continuously monitoring HCl formation were performed with PVC to determine the optimum temperature for HCl formation. Under conditions of maximum HCl formation, PVC was pyrolyzed with and without oxygen in a fluidized bed reactor and the formation of polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) measured. Avoiding the formation of these highly toxic compounds would be a critical element in any waste stream processing scheme. 

The Chemikalien-Verbotsverordnung lays down limit values for polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) which may not be exceeded in substances, preparations or articles manufactured in Germany or placed on the German market. The stringent limits are detailed in Table 23-9. 

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

Because of very high toxicity, ability of delayed action and high stability in the environment, polychlorinated dibenzodioxins (PCDD), dibenzofurans (PCDF) and biphenyls (PCB) are particularly hazardous for people s health if misused for committing acts of terrorism, or under the circumstances of violating the rules of toxic wastes safe storage. 

Polychlorinated dibenzodioxins (PCDDs) Polychlorinated dibenzofurans (PCDFs) Polychlorinated biphenyls (PCBs) Polyaromatic hydrocarbons (PAHs) Pentachlorophenol Short chain chlorinated paraffins Hexachlorocyclohexane isomers Mercury and organic mercury compounds Cadmium... 

There are 75 possible isomers of polychlorinated-p-dibenzodioxin (PCDD) and 135 such isomers of polychlorinated dibenzofuran (PCDF). These related compounds are known as congeners. In addition, PCBs form a similar group of 209 related congeners that differ only in the number and pattern of chlorine atoms attached to the parent biphenyl molecule. 

The sources of unintentionally produced POP chemicals, polychlorinated dibenzodioxins (PCDD), polychlorinated dibenzofurans (PCDF), and hexachlorobenzene (HCB), has been estimated through the National Implementation Plan (NIP) for Malaysia. However, an official report has not been made public. The draft final report on the assessment of unintentionally produced chemicals conducted by Universiti Sains Malaysia... 

Another major exposure route for humans is via contaminated food. For example, North America s Great Lakes, which are the largest body of freshwater in the world, are polluted with about 362 contaminants that were found in quantifiable amounts in the water, sediment, and biota (IJC 1983 USEPA 1994). The critical pollutants were identified as PCBs, DDT, dieldrin, toxaphene, mirex, methyl mercury, benzofa) pyrene, hexachlorobenzene, polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and alkylated lead. Some of these pollutants biomagnify in the aquatic food chain and can be detected in increased levels in cooked Great Lakes fish. Consequently, the blood serum levels of these chemicals are significantly increased in consumers of contaminated Great Lakes sport fish compared to people who do not eat such fish (Flumphrey 1983 Fiore et al. 1989 Sonzogni et al. 1991). 

Rieger R, Ballschmiter K (1995), Fresenius J. Anal. Chem. 352 715-724. Semivolatile organic compounds - polychlorinated dibenzodioxins (PCDD), polychlorinated dibenzofurans (PCDF), polychlorinated biphenyls (PCB), hexachlorobenzene (HCB), 4,4 -DDE, and chlorinated paraffins (CP) - as markers in sewers films"... 

Dioxin A family of chemicals with related properties and toxicity. There are 75 different dioxins, or polychlorinated dibenzodioxins (PCDDs) 135 different furans, or polychlorinated dibenzofurans (PCDFs) and 209 different polychlorinated biphenyls (PCBs). Each different form is called a congener, a member of a family of compounds known chemically as dibenzo-p-dioxins. Concern about them arises from their potential toxicity as contaminants in commercial products. Tests on laboratory animals indicate that it is one of the more toxic anthropogenic (man-made) compounds a term used interchangeably with 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD Disease prevention Measures used to prevent a disease or reduce its severity Dispersoids The particles of a dispersion... 

Polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are chemically classified as halogenated aromatic hydrocarbons. The chlorinated and brominated dibenzodioxins and dibenzofurans are tricyclic aromatic compounds with similar physical and chemical properties, and both classes are similar structurally. Certain of the PCBs (the so-called coplanar or mono-ortho coplanar congeners) are also structurally and conformationally similar. The most widely studied of these compounds is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This compound, often called simply dioxin, represents the reference compound for this class of compounds. The structure of TCDD and several related compounds is shown in Figure 4.1. 

The severe health effects observed in the Japanese Yusho incident of 1968 were attributed to the ingestion of polychlorinated biphenyls (PCBs). At that time, the forefront of analytical chemistry was represented by the determination of trace components at the parts per million (ppm) concentration level. It was not until about ten years later that analytical methodology was able to detect polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs) at concentrations of 10 parts per billion (ppb) or less in the presence of PCBs. The significance of the determinations lies in the assessment of risk to human populations exposed to undegraded PCBs and to mixtures of chemically similar compounds of concern derived from uncontrolled reactions such as might occur when a PCB filled transformer undergoes eventful failure. 

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