Dioxins sources

Abbreviations. LD, lethal dose TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin. Source Data from Loomis TA, Hayes AW. Loomis s Essentials of Toxicology. 4th ed. San Diego Academic Press, 1996. 

In addition to those sources discussed above, there are various other sources that could release considerable amount of dioxins. For instance, power/energy generation, non-ferrous metal processes, medical waste incineration, transportation, and cement kilns are all potentially significant dioxin sources, according to the experiences of other countries. However, there are no related data reported in China. 

The above estimates suggest that there may be significant unidentified sources of PCDD/Fs. This possibility is highlighted by Rigo,13 who assigns 82% of total annual emissions in the US to other, unidentified and natural sources, and by Travis and Hattemer-Frey,34 who have estimated that as much as 90% of total TCDD input into the US environment is unaccounted for by specific sources. This view is questioned by Thomas and Spiro,59 who believe that careful analysis of dioxin emissions provides no evidence for significant missing dioxin sources. 

The presence of oxygenated polyaromatic compounds in the product gas is inqjortant because they can act as dioxin sources. Aside for dibenzofuran, the analysis instrument was not calibrated for quantification of other oxygenated poly aromatic compounds. In the gas from LU-gasifier, dibenzofuran stands for between 0.5 and 1.5 %wt. of the total PAHs, The corresponding value for the V5mamo gasifier is considerably less and in most cases dibenzofuran does not exist in the gas. However to be able to study the effect of different parameters on behaviour of these conq>ounds the ratio between the peak area for oxygenated compound and peak area of the dibenzofuran were calculated. These calculated values are presented in Table 5. 

At present, municipal incinerators, hazardous waste incinerators, and metal smelters discharge from 1-100 ng/Nm of PCDD, about 1-100 g/year per facility. The possibility of PCDD in exhaust emissions from cars has been raised recently, and the U.S. Environmental Protection Agency (EPA) has examined a range of other possible dioxin sources. 

KuUcarni, P., Crespo, J. and Afonso, C. (2008). Dioxins sources and current remediation technologies — A review, Environ. International, 34, pp. 139-153. 

For a detailed discussion of the sources and biological effects of doxins see the article Dioxins Not Doomsday in the December 1999 issue of the Journal of Chemical Education pp 1662-1666... 

The proposed mechanism by which chlorinated dioxins and furans form has shifted from one of incomplete destmction of the waste to one of low temperature, downstream formation on fly ash particles (33). Two mechanisms are proposed, a de novo synthesis, in which PCDD and PCDF are formed from organic carbon sources and Cl in the presence of metal catalysts, and a more direct synthesis from chlorinated organic precursors, again involving heterogeneous catalysis. Bench-scale tests suggest that the optimum temperature for PCDD and PCDF formation in the presence of fly ash is roughly 300°C. 

Of great concern for air pollution problems resulting from the incident are dioxin-like compounds. In general, dioxin-like compounds can be generated when chlorine donor compounds are present. Depending on the source of the coal tar, chlorine content may range between 1 and 5000 ppm. 

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

Natural gas will continue to be substituted for oil and coal as primary energy source in order to reduce emissions of noxious combustion products particulates (soot), unburned hydrocarbons, dioxins, sulfur and nitrogen oxides (sources of acid rain and snow), and toxic carbon monoxide, as well as carbon dioxide, which is believed to be the chief greenhouse gas responsible for global warming. Policy implemented to curtail carbon emissions based on the perceived threat could dramatically accelerate the switch to natural gas. 

Rappe, C., Nygren, M., and Linstrom, G. et al. (1987). Overview on environmental fate of chlorinated dioxins and dibenzofurans sources levels and isomeric pattern in various matrices. Chemosphere 16, 1603-1618. 

U.S. ERA. An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States for the Years 1987, 1995, and 2000 (EPA/600/P-03/002f, Final Report, November 2006). U.S. Enviroiunental Protection Agency, Washington, DC, EPA/600/P-03/002F. 

Yunker, M.B. and Cretney, W.J. (1996). Dioxins and furans in crab hepatopancreas uses of principle component analysis to classify congener patterns and determine linkages to contamination sources. In M. Servos, K.R. Munkittrick J H. Carey, and G.J. van der Kraak (Eds.) Environmental Fate and Effects of Pulp and Paper Mill Effluents. Delray Beach, FL St. Lucie Press, pp. 315-325. 

Purification of the radioactive tracer was modified to include a fractional sublimation before a single extraction—recrystallization cycle to conserve the tracer material. Microgram samples were prepared in melting point capillaries for assay by mass spectroscopic analysis (Table III), made by direct probe injection of the sample into the ion source (18). The probe was heated rapidly to 200°C, and mass spectra were obtained during vaporization of the sample. Tri-, tetra-, and pentachlorodibenzo-p-dioxins vaporized simultaneously with no observed fractionation. 

A consistent pericardial edema in chickens gave rise to the term chick edema disease (chick edema factor) (I). Two known outbreaks of the disease in the broiler industry resulted in a great loss of chickens. A lipid residue from the manufacturing fatty acids, being used as a feed ingredient, was a principal source of the toxic substance. Contamination of the lipid component with polychlorodibenzo-p-dioxins was attributed as the causal agent. 

Figure 1. Mass spectrum of 2,3,7,8-tetrachlorodihenzO -p-dioxin (TCDD). The molecular ion (M ) is at m/e 320. Ionizing voltage 70 eV, source 150" C. Asterisk denotes impurUy.

Light Source Exposure Time Oclachlorodibenzo-p-dioxin Formed Based on Total Sample Weight... 

Baker 11, RA Hites (2000) Is combustion the major source of polychlorinated dibenzo-/ - dioxins and diben-zofurans to the environment A mass balance study. Environ Sci Technol 34 2879-2886. 

Evers EHG, HJC Klamer, RWPM Laane, HAJ Covers (1993) Polychlorinated dibenzo- -dioxin and dibenzo-furan residues in estuarine and coastal North Sea sediments Sources and distribution. Environ Toxicol Chem 12 1583-1598. 

Polychloro-benzenes, polybromo-benzenes, and dioxins (TCDD) are among these compounds. They were discovered when the analysis techniques improved. Especially the development of GC-MS has contributed to the knowledge of the distribution of these compounds. Effects on humans are the development of chloracne, suppression of the immune system, and some compounds are probably carcinogens (Shaw 1993). As a consequence of the ubiquitous nature of PCBs, humans are exposed via many sources. 

To control the emission of organics, these units must comply with similar DRE requirements to the other hazardous waste combustion units. Owners or operators of MACT combustion units must select POHCs and demonstrate a DRE of 99.99% for each POHC in the hazardous wastestream. Sources that bum hazardous waste have a required DRE of 99.9999% for each POHC designated. Additionally, for dioxins and furans, U.S. EPA promulgated more stringent standards under MACT. For example, MACT incinerators and cement kilns that bum waste with dioxins and furans must not exceed an emission limitation of either 0.2 ng of toxicity equivalence per dry standard cubic meter (TEQ/m3) or 0.4 ng TEQ/m3 at the inlet to the dry particulate matter control device. This unit of measure is based on a method for assessing risks associated with exposures to dioxins and furans. 

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... 

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