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RISK CHARACTERIZATION OF DIOXINS
Citation:
BIRNBAUM, L. S. RISK CHARACTERIZATION OF DIOXINS . Presented at International Congress on Occupational Health, Milan, ITALY, June 11 - 16, 2006.
Description:
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD; "Dioxin") is the most toxic member of a family of structurally related compounds which are ubiquitous environmental pollutants. The most potent of these, the polyhalogenated dibenzo-p-dioxins and furans, were never produced intentionally, but are unwanted contaminants of certain industrial and combustion processes. The polyhalogenated biphenyls, napthalenes, and azo- and azoxybenzenes were made commercially, and specific isomers are dioxin-like in their properties. The major new sources of PCDDs and PCDFs today are uncontrolled incineration and other combustion processes. Other sources include metal refining and reservoir sources. Deposition worldwide is associated with atmospheric transport of new emissions as well as environmental recycling of contaminated soils and sediments. Their resistance to physical, chemical, and biological degradation has resulted in extreme persistence and biomaganification up the food chain.
Dioxins induce a broad spectrum of biological effects in multiple species mediated by a highly conserved cellular regulatory protein, the Ah receptor. Adverse effects in reproduction of fish, birds, and mammals in the wild have been linked to exposure to this class of chemicals. Poisoning incidents have led to loss of domestic animals including chickens, cattle, and horses. A plethora of effects have been observed in laboratory animals, ranging from lethality to subtle biochemical responses. Many of the effects are widely distributed, while others are more species, sex, organ, tissue, or age specific. Dioxin has been shown to immunotoxic, neurotoxic, developmentally toxic, hepatotoxic, dermally toxic, a reproductive toxicant, and carcinogenic. Similar effects have been reported in people. Although body burdens are decreasing, there is little margin of exposure. (This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.)