The word dioxin, technically known as chlorinated dibenzo dioxin, is used to describe a family of 75 compounds all similar in structure. Each compound contains two chlorinated benzene rings attached by one or two oxygen atoms. All dioxin compounds differ in toxicity levels, number of chlorine atoms, and location of the chlorine atoms. The level of toxicity of each dioxin varies due to the number of chlorine atoms it contains. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the variant most frequently referred to as dioxin, has the highest toxicity level.

Dioxins are formed by the presence of carbon, oxygen, hydrogen, chlorine, and heat, and therefore can be unwanted by-products of both manmade and natural processes. Greater amounts of dioxin are emitted from these processes when materials are burned inefficiently and at low temperatures (between 200 and 450 degrees Celsius). Dioxins are formed after the combustion process during the cooling of combustion by-products. Forest fires, brush fires, and volcanic eruptions are examples of processes that naturally emit dioxins. In the industrial field, dioxins are unintentional by-products of incineration, combustion, and pulp and paper bleaching. Dioxin emission also occurs from trash burning, pesticides, and landfill fires. Once dioxins are emitted, they travel through the atmosphere and accumulate in soil, sediment, and water. Since dioxins are highly stable and fat-loving compounds, they attach themselves to particles rich in organic matter. Through the ingestion of grass-grazing animals, dioxins bioaccumulate through the food chain in fat and milk.

Once dioxin enters a human body, that person is at greater risk for developing cancer, immune system difficulties, and reproductive and developmental problems. In women, dioxin exposure increases the risk of endometriosis and can also be spread to children, both prenatally and after birth. In men, dioxin exposure can decrease testosterone levels and lower sperm counts.

Although dioxin levels have decreased over 90% since the 1970s, dioxin's inability to readily breakdown still makes the toxic pollutant an area of concern. Since about 95% of dioxin exposure is through the food chain, preventive measures are still needed to keep dioxin out of our food supply and out of our bodies.

Source: www.eurochlor.org/chlorine/issues/dioxins.htm