Sources of Dioxin

A number of combustion and chemical production processes contribute to environmental concentrations of PCDD/F. Sources that have traditionally caused the greatest concern include municipal waste incinerators, hospital waste incinerators, bleached chemical wood pulp and paper mills, motor vehicles and wood combustion. We have attempted to represent the most recent data available on PCDD/F emissions from these sources. It should be remembered that the list presented here is by no means exhaustive. Potential sources of TCDD not discussed in the following paragraphs include discharges from metal processing and treatment plants, copper smelting plants and pentachlorophenol production. 

Municipal solid waste incinerators (MSWIs) are often thought to be the largest source of dioxin in the US.10 Approximately 176 MSWIs in the US11 combust 2.9 x 10lokg yr-1 of municipal solid waste.12 Applying an emission factor of 3.56 x 10 8 g TEQ kg-1 of municipal waste13 yields an estimate of 1032 g 

Halsalland K. C. Jones, presented at Dioxin 93,13th International Symposium on Chlorinated Dioxins and Related Compounds, Vienna, Austria, 1993. 

4 US Environmental Protection Agency, National Dioxin Study, EPA/530-SW-87-025, Office of Solid Waste and Emergency Response, Washington, 1987. 

7 US Environmental Protection Agency, National Study of Chemical Residues in Fish, EPA/832-R-02-008, Office of Science and Technology, Washington, 1992. 

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Dioxin and furan. During the late 1980s, bleaching with chlorine and hypochlorite were discovered to be a source of dioxin and furan. Although the use of chlorine dioxide (ClOj) bleaching minimizes the formation of chlorinated pollutants, measurable quantities of... 

TCP), and pentachlorophenol (PCP), in order of abundance. Minor amounts of other trichlorophenols and dichlorophenols may also be present, as well as recalcitrant polychlorinated phenoxyphenols (PCPPs) and PCDD/Fs as impurities [75, 76]. In Finland, approximately 30,000 tons of CP products were used between 1934 and 1988, when they were banned because of their potential toxicity to humans and the environment [77, 78]. The careless manufacturing and application of wood preservatives together with the lack of suitable waste disposal caused massive contamination of river sediments and sawmill sites. For example, the river Kymijoki in southern Finland was identified as the largest source of dioxins accumulating in fish in the entire Baltic area. Similar products were used in other European countries, especially Nordic countries with a large forestry industry, such as Sweden [79]. 

Incineration of domestic waste is also a contributor to environmental pollution. One more source of dioxins is pulp-and-paper industry. Comparatively new ways of forming polychlorinated dibenzo-p-dioxins and furans are high-temperature processes like copper melting in electric arc furnaces, and production of magnesium, nickel and, possibly, other metals of their chlorides. 

The presence of chlorine and chlorinated compounds is also the source of dioxins and furans during paper making, and these compounds have been detected in sediments in the vicinity of a pulp and paper mill [53] and in effluents, along with polychlorinated dibenzothiophenes [54]. A recent study found high concentrations of PCDD and PCDF along with PCP in nestling tissue (Tachycineta bicolor) collected downstream of paper pulp mills, suggesting that the primary source of contaminants was the use of PCP for timber preservation [55]. In addition, it has been shown that dioxins bioaccumulate in fish downstream of pulp and paper mills [56]. The levels of chlorinated compounds of different families are shown in Fig. 3. 

Critics of waste incineration argue that these plants often create more environmental problems than they solve. They point out, for example, that incinerators are a major source of dioxin, mercury, and halogenated hydrocarbon release into the atmosphere. In addition, incinerators are very expensive to build and to maintain, and they provide fewer jobs to members of the surrounding community than other methods of solid waste disposal. Also, companies have a dismal record of siting incinerators in disadvantaged communities, where residents suffer the worst consequences of incinerator use. Finally, waste-to-energy incinerators are of little value in tropical and subtropical countries, where the cost of plants and the availability of additional energy sources make them impractical. 

Micro-contaminants are present in chemicals at concentrations <1% of the mass. A very important class of micro-contaminants in a number of chlorinated chemicals is the chlorinated dioxins and furans. Dioxins are now classified as POPs [43], but in the late 1960s and early 1970s [201] became widely known when they were discovered to be micro-contaminants of 2,4,5-T-containing herbicides. There are numerous sources of dioxins but the most important source from synthetic chemicals is from... 

Meharg AA, Killham K (2003) A Pre-industrial Source of Dioxins and Furans. Nature 421 909... 

In several European countries, higher dioxin levels have been reported in eggs of free-range chickens, compared to chickens kept indoors (DeVries et al., 2006). High levels were found mostly on smaller farms, possibly because the chickens made more extensive use of the outdoor run. Plants appeared to be a relatively unimportant source of dioxins, as well as commercial feed. It was concluded that the high dioxin levels were related to the consumption of worms, insects and soil. 

In addition to the incineration processes, herbicides, CNP (2,4, 6-trichlorophenyl-4 -nitrophenyl ether) and PCP (pentachlorophenol) usage was reported as the major source of dioxins, especially during the late 1960s 1970s. While CNP contained particular non-toxic dioxin congeners such as 1,3,6,8-TeCDD and 1,3,7,9-TeCDD (Yamagishi et al.,... 

US EPA, 1998b. The Inventory of Sources of Dioxin in the United States. EPA/600/P-98/ 002Aa. Washington D.C. 

For release to land , the only category with an EF available was Uncontrolled Combustion Processes . Burning of biomass in forest/ grassland fires contributed to the total annual land dioxin/furan release of 0.05 g TEQ. There was a general lack of information on other potential local land sources of dioxin/furan release. 

Based on the activities that were initially conducted for the enabling activity project (Bravante and Medina, 2004), it was reported that little is known about POPs in the country and that even the users have minimal understanding of their hazards. As no comprehensive data on POPs is available for use as baseline information, a more comprehensive inventory is needed for the Philippines to have an actual measure of the risks that must be managed and addressed in the NIP. The Initial National Inventory conducted showed that POPs have already been banned in the country except HCB and mirex, which have no recorded use, importation or production in the country. Significant amounts of PCBs mainly come from electric transformers and capacitors. Dioxins and Source Inventory by DOST showed that there are numerous sources of dioxins and furans in the country, which emit significant quantities of dioxins and furans into the environment. No treatment facility in the country that deals with the destruction of POPs and other toxic hazardous wastes are present in the country (Bravante and Moreno, 2005). 

Dioxins (PCDDs) occur as contaminants in many agricultural pesticides and can occur in the environment as a result of pesticide usage, although many other industrial sources and natural sources have been identified. The National Dioxins Program (2004) has revealed that major sources of dioxins in the environment are uncontrolled combustion sources such as bush fires and accidental fires which contribute 70% of the total to the air and 80% to the soil whereas waste disposal and land filling contribute 75% of the total to water. 

Schaum J, Cleverly D, Lorber M, et al. 1994. Updated analysis of US. sources of dioxin-like compounds and background exposure levels. Organohalogen Compounds 20 178-184. 

Schecter A, Dekin A, Weerasinghe NCA, et al. 1988. Sources of dioxins in the environment A study of PCDDs and PCDFs in ancient, frozen Eskimo tissue. Chemosphere 17 627-631. 

Tong H, Gross M, Schecter A, et al. 1990. Sources of dioxins in the environment Second stage study of PCDDs/PCDFs in ancient human tissue and environmental samples. Chemosphere 20 987-992. 

The goal of this chapter is to identify the major sources of dioxin and related compounds, to identify the major pathways of human exposure and to estimate the extent of the resulting human exposure. 

Ambient measurements confirm that environmental PCDD/F contamination is widespread and that virtually everyone - regardless of age, gender, or geographic location-is exposed to these compounds on a daily basis. We identify MSW incinerators as the major known source (48%) of environmental PCDD/Fs, followed by cement kilns, medical waste incinerators, wood combustion and pulp and paper mills. However, these known sources appear to account for only a fraction (10-30%) of the total annual atmospheric deposition of PCDD/Fs in the US. Thus, either significant unidentified sources of dioxin exist or most dioxin presently circulating in the atmosphere results from re-suspension and/or volatilization of historically deposited dioxin. 

Buser HR (1992), Chemosphere 25 45-48.. .Identification and sources of dioxin-like compounds - I. Polychlorodibenzothiophenes and polychloiothianthrenes, the sulfur-analogues of the polychlorodibenzofurans and polychlorodibenzodioxins"... 

Sources of dioxin emissions in the Netherlands", Eds. Umweltbundesamt, Wien, Osterreich Eduljee GH (1988), Chemistry in Britain 60 1223-1226. Dioxins in the environment"... 

U.S. Environmental Protection Agency, Locating and Estimating Air Emissions from Sources of Dioxins and Furans (May 1997). http //www.epa.gov/ttnchiel/le/dioxin.pdf... 

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