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Krótki kurs historii POP. Część trzecia : dioksyny

Mastalerz P.

Wiadomości Chemiczne

2004

[Z] 58, 3-4

293--337

Dioxins as a class of chemical compounds were defined with consideration of their biological properties rather than structure of molecules. Their structures are quite diverse and include all chlorinated dibenzodioxins and dibenzofurans as well as some chlorinated biphenyls. The common feature of several (but not all) dioxins is their pronounced toxicity to animals. The best known and most toxic is the 2,3,7,8-tetrachlorodibenzodioxin, simply referred to as dioxin or TCDD. Dioxins are produced by virtually all industrial processes involving organic matter and chlorine at elevated temperatures. In the past the incineration of communal wastes was a particularly important source of dioxin but gases emitted by modern waste incinerators do contain less TCDD than ambient air. For many years it was believed that dioxins are man-made compounds without natural sources but that belief was disproved by the discovery of TCDD in forty million years old clay deposits. Evidence is mounting that forest fires and burning of coal, wood and peat in domestic hearths are the most important sources of dioxins. A dioxin-free world is not possible because man has little control over forest fires and there is no way to curtail the burning of dioxin-producing fuels in homes, partricularly in poor countries. Dioxins are in our bodies and around us. The fat of humans not exposed to large concentrations of dioxins contains TCDD at concentrations of several pg/g. The dioxin levels in the air are at the level of several pg/m3. Concentrations larger by orders of magnitude are in soils around the world and in sediments and sewage sludges. Dioxins in human bodies are derived from the food we eat. The concentrations in food vary within wide limits, from less than 1 pg/g in vegetables to more than 100 pg/g in some fishes. There are scientists who express grave concern over possible harmful effects of dioxins in food but scientific evidence demostrates that such concerns are totally unfounded. After all the dioxins were on our planet since the beginning of mankind and even before and nobody was ever able to provide evidence of their harmfulness. On the contrary, there are many examples of highly exposed industrial workers who suffered no adverse effects although their blood contained several hundred times more dioxins than the blood of the general population. It is commonly believed that TCDD is the most toxic man-made compound, is highly carcinogenic and presents a very serious risk to human health. These are unfounded beliefs without any support by scientific evidence. The only demonstrated dioxin-related human disease is chloracne, a skin disease associated with heavy exposure to TCDD. In some cases chloracne persists for one or two years but never threatens the life of victims. Medicine knows of no case of human death due to dioxins. This simple fact strongly contradicts the belief that dioxins are deadly poisonous to humans.