Dioxins in the food chain Prevention and control of contamination

What are dioxins? The common term dioxins is often used for a number of chemically related lipophilic compounds (polychlorinated dibenzo-para dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), including certain dioxin-like polychlorinated biphenyls (PCBs) with similar toxic properties. However, the denomination of dioxin is given to 2,3,7,8-tetrachloro-dibenzo-para-dioxin (TCDD). Of the identified 4 9 types of dioxin-related compounds, which have a dioxin-like chemical structure, only about 30 are considered to have significant toxicity, with TCDD being the most toxic. Although dioxins and dioxin-like PCBs (for convenience herein after referred to as “dioxins”) show similarities in their toxicological and chemical behaviour, their sources may be different. Dioxins are pervasive environmental pollutants. They are often referred to as persistent organic pollutants because they are resistant to both physicochemical and biological degradation decompose very slowly and remain in the environment for long periods of time because of their chemical stability. Dioxins, once entered in biological organisms including humans, accumulate in the fat tissues. For TCDD, the half-life in the body is estimated to be seven to eleven years, but other dioxins have variable half-lives. Dioxins have a highly toxic potential because they affect a number of organs and systems and bio-accumulate along the food chain. Although formation of dioxins is local, environmental distribution is global. Dioxins are found throughout the world in practically all media. The highest levels of these compounds are found in soils, sediments and food, especially dairy products, meat, fish and shellfish. Very low levels are found in plants, water and air.