Dioxins
Author: Dr Kelvin Klemm
( Article Type: Explanation )
Dioxin refers to a group of chemical compounds that share certain similar chemical structures and biological characteristics. There are several hundred of these toxic compounds that are members of related families. The families are complex chemicals with complex names such as chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs) and polychlorinated biphenyls (PCBs). The most well-known dioxin is 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) and sometimes the term ‘dioxin’ is used to refer to TCDD only. Dioxins such as CDDs, CDFs, and PCBs were created intentionally for industrial purposes, but others are created unintentionally from processes such as the incineration of waste, the burning of fossil fuels, and the chlorine bleaching of pulp and paper. Cigarette smoke also contains small amounts of dioxins. Dioxins are also produced in nature in forest fires and volcanoes.
Dioxins are extremely persistent compounds. When released into water they tend to settle and can then be further ingested by fish or aquatic organisms. Dioxins can also be deposited on plants and be taken up by animals and other organisms.
Different dioxins have different toxicities, but mostly they are found in a mix rather than as single compounds. The most noted health effect in people exposed to large amounts of dioxin is chloracne. This is a skin disease with acne-like lesions. Other effects of exposure to large amounts of dioxin include skin rashes and skin discolouration.
Another concern is that exposure to small amounts of dioxin could cause cancer in adults who were exposed to dioxins in the work place for many years. Most of the population has low level exposure to dioxins, and it has been estimated that over 95% of such exposure comes through the dietary intake of animal fats. Dioxin is also found in small quantities in the soil.
First world countries have moved to reduce the amount of dioxins in the environment by controlling industrial use (e.g. PCBs have been banned), and ensuring high temperature incineration of certain wastes to optimise complete burning, thereby ensuring that dioxins are not inadvertently produced as a by-product of incomplete incineration.
