Dioxins and Dioxin-like PCBs in Feed and Food

Abstract

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) which are often together termed "dioxins" are two classes of environmental contaminants comprising 210 congeners that were never produced industrially but are formed as unwanted by-products in a number of industrial and thermal processes. In contrast, since their first commercial introduction in 1929, polychlorinated biphenyls (PCBs) had found wide-spread applications in open and closed systems due to their specific physico-chemical properties. PCBs cover 209 different congeners and can be divided into two groups. Those compounds that are non-ortho or mono-ortho substituted with chlorines can adopt a comparable spatial alignment as dioxins, exhibit similar toxic properties and thus are called "dioxin-like PCBs (DL-PCBs)". Congeners with more than one chlorine atom in the ortho-positions are termed "non dioxin-like PCBs (NDL-PCBs)". Dioxins and PCBs are lipophilic contaminants that are stored in fatty tissues and are accumulated in the food chain. In this respect, the contamination of feed is of special importance. For the general population, consumption of food, especially products of animal origin, represents the major pathway of exposure. Due to measures aiming at reduction of dioxin emissions and closing of known sources as well as strict Regulations on PCBs, human exposure with these contaminants has decreased substantially during the past 30 years. However, due to criminal or grossly negligent actions of individuals, a number of incidents occurred in the past two decades causing massive feed contamination and subsequent food adulteration which foiled the successful measures to reduce human exposure with dioxins and PCBs.