https://doi.org/10.15255/KUI.2001.033
Published: Kem. Ind. 51 (6) (2002) 267–280
Paper reference number: KUI-33/2001
Paper type: Review

Dioxins – Summary of Recent Knowledge

M. Mazalović, M. Kovčalija, L. Tinjić, E. Mazalović, Z. Žigić, L. Begić and S. Berbić

Abstract

Since accident in Seves, Italy, which took place in 1976, dioxins are inevitable topic while thinking about prevention of emission of toxic chemicals into environment. This is a review of today's knowledge about dioxins - highly toxic chemicals, harmful for environment. Dioxins are chemical compounds produced by man, during different industrial procedures of production and processing of organic matters, they are not natural products and therefore it is very important to locate possible sources of these potential pollutants. According to the current knowledge about mechanism of synthesis of polyhalogenated dibenzodioxins and dibenzofurans, they could arise as the side products of different industrial processes; the most important among them is burning of household trash and other organic waste. Dioxins are formed by the combustion of virtually all organic substances in presence of either chlorine or its organic or inorganic compounds. In this paper, seven most important mechanisms of dioxin/furan synthesis are shown, all of them could occur in different industrial productions and processings of organic compounds. TetraChloroDibenzo-p-Dioxin (2, 3, 7, 8 TCDD) or "Seveso" dioxin or simply "dioxin" is the most toxic synthetic chemical on the Earth; more toxic than cyanide-ion, strychnine or a nerve-gas. It is very stable aromatic compound characterized by very high biological persistency. During natural processes it remains almost intact, that means that its quantity in the environment may only rise, if appropriate reaction is absent. Chemical degradation half-time of dioxin in human body is estimated to 6-10 years. Data about chemical dissolution of dioxin in atmosphere, at water surface, in soil, and in sediment are also quoted in this paper. While degradation of dioxin is not observed in the sediment, at the same time its chemical degradation half-time in the air is from 42 hours up to 32 days, at the water surface 600 days, and in the soil from 2 up to 9 years. Data about its harmfulness to human health are given in short form. Although chlorine acnes are the first indications of poisoning, especially by acute poisoning with dioxin and some other polyhalogenized aromatic compounds, even more important are carcinogenic effects and harmful influence on reproduction. What international community undertakes in order to reduce emission of dioxins into environment is also described in this paper. According to adopted position of international association: UNEP (The United Nations Environment Program), EPA (Environment Protection Agency), Green Movement, and others, polychlorinated organic compounds are the most toxic synthetic chemicals in human environment. Until the end of year 2001 these chemicals should be either entirely eliminated from, or their concentration should be strongly reduced in ecological environment. Polyhalogenated organic compounds are classified by toxic effect into 12 classes: PolyChlorinatedDibenzoDioxins - PCDDs, PolyChlorinatedDibenzoFurans - PCDFs, PolyBrominated DibenzoDioxins/Furans- PBrDDs/Fs, mixed PolyChlorinated- PolyBrominatedDibenzoDioxins/Furans- PXDDs/Fs; PolyChlorinatedBiphenyls - PCBs, polychlorinated "hard" insecticides: HexaChloroCycloHexan - HCH, DichloroDiphenylTrichloroethan - DDT, Chlordane, Toxaphens, Dieldrin, Endrin, Heptachlor, Mirex and Kepone. As of year 1970, EPA has banned use of DDT, aldrin, dieldrin and chlordane, because of their carcinogenic effect. The most important characteristics of these compounds and their chemical structures are described in this paper. Measures taken by international community, which include the cease of chemical productions which may generate dioxins/furans (PolyChlorinatedBiphenyls - PCBs, pentachlorophenol - PCP, 2,4,5 - Trichlorophenoxy acetic acid) were already successful. Level of dioxin in some parts of human environment (sediment) as well as in some biological systems is considerably lower in last 10 - 15 years. Researches conducted in Germany, in period from 1986 to 1994 have unveiled a great decrease (two to three times) of PCDD/F compounds concentrations in biological matrices (cow's milk, human milk, blood, adipose tissue).

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Keywords

toxic chemicals in human environment, polyhalogenized aromatic compounds, polychlorinated-dibenzodioxins/furans, 2,3,7,8-tetrachlordibenzodioxin, chlorinated pesticids, dioxin generation mechanisms in industrial processes, combustion of household trash and other organic waste, toxicity of dioxin, factor of equivalent toxicity, carcinogenic effect