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December 12, 2004

What are dioxins? Why the concern?

Topics: Medicine

Owing to the Yushchenko poisoning by Dioxin, a Dec 12 Medical News Today article might be of interest to some of you who may not understand what all the fuss is about.

'Dioxins' refers to a group of chemical compounds that share certain chemical structures and biological characteristics. Several hundred of these compounds exist and are members of three closely related families: the chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs) and certain polychlorinated biphenyls (PCBs). Sometimes the term dioxin is also used to refer to the most studied and one of the most toxic dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). CDDs and CDFs are not created intentionally, but are produced inadvertently by a number of human activities. Natural processes also produce CDDs and CDFs. PCBs are manufactured products, but they are no longer produced in the United States.

Dioxins are formed as a result of combustion processes such as commercial or municipal waste incineration and from burning fuels (like wood, coal or oil). The draft dioxin reassessment makes the finding that anthropogenic emissions dominate current releases in the United States, but acknowledges the need for more data on natural sources. Dioxins can also be formed when household trash is burned and as a result of natural processes such as forest fires. Chlorine bleaching of pulp and paper, certain types of chemical manufacturing and processing, and other industrial processes all can create small quantities of dioxins. Cigarette smoke also contains small amounts of dioxins.

(...)    Studies have shown that exposure to dioxins at high enough doses may cause a number of adverse health effects. Because dioxins from natural and anthropogenic sources have been widely distributed in exist throughout the environment since the early 1900's (and before), almost every living creature, including humans, has been exposed to dioxins. (See G9) The health effects associated with dioxins depend on a variety of factors including: the level of exposure, when someone was exposed, and how long and how often. Because dioxins are so widespread, we all have some level of dioxins in our bodies.

(...)    The most common health effect in people exposed to large amounts of dioxin is chloracne. Such levels have typically been the result of accidents or significant contamination events. Chloracne is a severe skin disease with acne-like lesions that occur mainly on the face and upper body. Other effects of exposure to large amounts of dioxin include skin rashes, skin discoloration, excessive body hair, and possibly mild liver damage.

(...)    One of the main health effects in question for dioxins is the risk of cancer in adults. Several studies suggest that workers exposed to high levels of dioxins at their workplace over many years have an increased risk of cancer. Animal studies have also shown an increased risk of cancer from long-term exposure to dioxins.   Read More...

From my prevous post on the topic I pointed out that in a May 1985 study involving rhesus macaques (Macaca mulatta), consumption of food containing commercial polychlorinated biphenyl (PCB) mixtures, some pure polychlorobiphenyl congeners, 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD), and 2,3,7,8-tetrachlorodibenzofuran (TCDF) caused the same clinical toxic manifestations and histopathologic lesions, although the potencies of the toxicants covered a range of five orders of magnitude.

Further, that of particular interest to Mr Yushchenko is the fact that recovery from poisoning by 3,4,3',4'-tetrachlorobiphenyl (34TCB) or TCDF was rapid, whereas recovery from poisoning by Aroclor 1242, 3,4,5,3', 4', 5'-hexachlorobiphenyl (345HCB) or TCDD(Dioxin) was protracted, if it occurred at all. Of course we haven't begun to talk about the carcinogenic aspects of his problem.  Environ Health Perspect. 1985 May;60:77-88   PMID: 3161723.

Posted by Hyscience at December 12, 2004 11:56 AM



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