The discovery of the insecticidal properties of DDT by Paul Müller (Läuger et al. 1944; DDT was synthesized more than 50 years ago (Zeidler 1874) can be deemed as one of the starting points of intensive search of organic compounds to be used as pesticides. These organic compounds were – and are – used and applied deliberately especially in the environment due to their properties as poisons against plants, fungi or insects. However, already in the beginning of the 1950s of the last century the persistence (i.e., high lifetime) of these compounds in the environment was realized and culminated 1962 in the publication of ‘Silent Spring’ by Carson (2000; Marco et al. 1987). Besides these highly chlorinated pesticides of the first generation, high amounts of chemically bad characterized mixtures such as polychlorinated biphenyls (PCB) were often used. Although these substances and further byproducts, such as chlorinated dibenzodioxins and dibenzofurans (as far as we know never used commercially), are from a chemical point of view not a homogenous group, besides other general properties, they are man-made and known to be at least persistent in the environment. As a consequence, these organic compounds were termed Persistent Organic Pollutants (POP).