The oceans, lakes and soils are huge reservoirs of previously released POPs. Although it is difficult to generalize, environmental and health authorities are most concerned about POPs in two types of circumstances where the properties of POPs have led to high levels in some top predator species. The first is in areas with a hinterland history of high POP release such as the Baltic, North Sea, Mediterranean Sea, and the Great Lakes of North America. The second is in regions where the properties of POPs alone, with no significant local sources, are responsible for the occurrence of similarly high levels. For example, in some of the Arctic marine species, which are a significant part of the diet of indigenous people, biomagnification and other ecological and life-cycle factors are responsible for the levels of POPs, which are of concern to health authorities.
Most POPs are man-made.
Examples include some industrial substances such as PCBs, many first-generation pesticides, including DDT, Chlordane, and Toxaphene, and several unintentionally produced substances, such as Dioxins, Furans, and PAHs, which result from the combustion of a wide range of common substances and materials. Because the primary mode of rapid dispersal of POPs around the world is through the atmosphere, the Convention on Long-range Transboundary Air Pollution is the ideal instrument to initiate international cooperation to control these substances. The basic obligations of the Protocol stipulate a wide range of actions ranging from production and use bans and phase-outs, restricted uses and emission controls, and conditions for the disposal of POPs. The Convention covers 42 countries in the northern hemisphere and the European Community, all of which will be free to sign the POPs Protocol. Many studies have indicated the presence of important sources of POPs within this area.