Persistent organic pollutants, a group of PTBs which are capable of long-range transport and deposition; they are believed to be transported primarily in the atmosphere. These have global effects. Most are already banned in Western Europe but some are still in use in developing countries. The POPs include the following 12: PCBs, dioxins and furans, aldrin, dieldrin, DDT, endrin, chlordane, hexachlorobenzene, Mirex, toxaphene and heptachlor. They fall into three groups: chlorinated pesticides; industrial chemicals; and emissions and by-products. POPs and other PTBs are being examined by various national, regional and international bodies with the aim of developing management strategies.