Chemical waste, PCDDs/PCDFs

Primary sources of environmental contamination with PCDD/PCDFs in the past were the production and use of organic chemicals containing chlorine. PCDFs were formed as inadvertent by-products in the production and use of PCBs and, in combination with PCDDs, in such high-temperature processes as waste incineration, the metal industry, home heating and other energy production processes. 

PCDFs are also found in residual waste from the production of vinyl chloride and the chlor-alkali process for chlorine production. Factors favourable for the formation of PCDD/PCDFs are high temperatures, alkaline media, the presence of ultraviolet light, and the presence of radicals in the reaction mixture/chemical process (Fiedler, 1999 Hutzinger and Fiedler 1993). 

Previous production of pentachlorophenol, as well as the bleaching process in pulp and paper mills, has been shown to be a major source. Changes in industrial processes have resulted in a reduction of PCDD/PCDFs concentration in products. Whereas in the past the chemical industry and, to a lesser extent, the pulp and paper industry were considered to be the main sources of PCDD/PCDFs (and also the cause of many of today s contaminated sites in several industrialized countries), today s dioxin input is mainly due to thermal processes. There is still a considerable focus on waste incineration but, owing to requirements for dioxin reduction in stack gases set by several national authorities, the importance of this category has declined during the last years. Examples can be seen especially in the European emission inventories... 

Secondary sources of PCDD/PCDFs, their reservoirs, are those matrices where they are already present, either in the environment or as products. Product reservoirs include PCP-treated wood, PCB-containing transformers and sewage sludge, compost and liquid manure, which can be used as fertilizers in agriculture and gardens. Reservoirs in the environment are, for example, landfills and waste dumps, contaminated soils (mainly from former chemical production or handling sites), and contaminated sediments (especially in harbours and rivers with industries discharging directly to the waterways). 

UK surveys of cows milk from individual farms near to potential industrial point sources of PCDDs and PCDFs, such as steelworks and waste incinerators, have shown few indications of concentrations elevated above the expected range for the UK, apart from a few sites where there was known pollution. These sites included Bolsover in Derbyshire where it is likely that localised pollution of agricultural land and associated streams occurred from a nearby incinerator that was used to dispose of chlorinated chemical waste.40 Some farms with elevated levels of PCDDs and PCDFs were also found close to the site of a former municipal waste incinerator.53 Both sites have been the subject of continued monitoring to ensure that no risk was posed to local consumers. 

If the toxicity equivalence is less than 0.7 parts per billion (ppb) for a soil or fly ash sample, less than 7 parts-per-trillion (ppt) for an aqueous sample, or less than 7 ppb for a chemical waste, no further analysis is required. If the toxicity equivalence is greater than or equal to 0.7 ppb (soil or fly ash), 7 ppt (aqueous), or 7 ppb (chemical waste), analysis on a column capable of resolving all 2,3,7,8-substituted PCDDs/PCDFs is required. 

CAUTION The analysis for PCDDs/PCDFs in water samples is for much lower concentrations than in soil/sediment, fly ash, or chemical waste samples. Extreme care must be taken to prevent cross-contamination between soil/sediment, fly ash, chemical waste and water samples. Therefore, it is strongly recommended that separate glassware be reserved for analyzing water samples. 

Liability for possession and production of persistent toxic chemicals, particularly PCDD and PCDF is going to increase. In Ontario the recent promulgation of the "Spills Bill" has placed the liability for immediate cleanup and damages for a spill of toxic chemicals directly on the transporter and producer. This bill will eventually increase the cost of transportation of waste and promote on-site destruction devices. 

Dioxins are produced inadvertently as a by-product of chemical production or during combustion and are widespread pollutants in the environment. They are ubiquitous. The biggest source of PCDDs, PCDFs, and PCBs is the large-scale burning of municipal and medical waste. Other sources include ... 

At the same time the issues related to the unintentionally produced dioxins and furans, i.e., polychlorinated dibenzo- -dioxins (PCDDs) and PCDFs, attracted public attention in 1983 when investigations revealed that dioxins were detected in the fly ashes from municipal waste incinerators. Therefore, measures to monitor dioxins in the bottom sediment and aquatic animals and plants in the rivers, lakes, marshes and seawaters as well as the atmosphere were initiated in 1986. Investigations were implemented on the actual status of waste incinerators in 1984 and pulp and paper factories in 1990. On the basis of these findings, guidelines and administrative guidance on controlling emissions of dioxin-related chemicals were derived and established. 

Fly ash from municipal waste and industrial waste incinerators contains polychlorinated dibenzo-p-dioxins (PCDDs), including tetrachlorodibenzo-/j-dioxin (TCDD) and polychlorinated dibenzofurans (PCDFs), which are lipophiles, and heavy metals, including chromium, copper, manganese, vanadium, and lead, which are hydrophilesJ29-31 These chemicals have multiple toxicities and are known to impact the human liver, immune system, respiratory system, thyroid, male reproductive function, and CNS J32 34l Several are human carcinogensJ32 35 Enhanced toxic effects are observed in the mixtures of some of theseJ21,22 36 The mixtures of toxicants present in fly ash are complex and the mechanisms for their action on the human body are largely unknown. It is known that occupational exposure to fly... 

Polychlorodibenzo-p-dioxins (PCDDs) and poly-chlorodibenzofurans (PCDFs) are mostly produced by incineration, although they are also a waste product of the pulp/paper and chemical manufacturing industries (Duarte-Davidson et al. 1997).There are potentially 75 PCDD and 135 PCDF congeners (see Fig. 7.17), but PCDDs from most biological samples contain only the tetra- to octachloro congeners with 2,3,7,8 chlorination the absence of the other congeners has been attributed to rapid metabolism and excretion (Ahlborg... 

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]. 

PCDDs and PCDFs constitute a class of ubiquitous pollutants with aromatic structure, high chemical stability and extremely poor water solubility. They can occiu in the form of 75 PCDD congeners and 135 PCDF congeners (Table 1). At present, most PCDD and PCDF soinces are well characterized. These sources include chemical, thermal, photochemical and enzymatic reactions. Combustion processes, mainly incineration plants such as municipal solid waste incinerators, clinical waste incinerators and industrial waste incinerators are known to be some of the most important sources responsible for the presence of these contaminants in the environment. Soils and sedi-... 

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are the most hazardous environmental pollutants that have received prolonged attention by the scientific community and by environmental regulation. These compounds are not commercially produced but can be formed during combustion processes, such as municipal waste incineration, in which halogenated compounds are exposed to very high temperatures. Other primary sources of formation of these compounds are related to various chemical processes that result in contaminated products and waste. Although there are theoretically 75 PCDFs and 135 PCDDs, only 17 of them... 

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