Progress in the studies associated with formation and emission of unintentionally produced persistent organic pollutants

Polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polychlorinated naphthalenes, pentachlorobenzene and hexachlorobenzene could be unintentionally produced and released during many industrial processes, and often termed as unintentionally produced persistent organic pollutants (UP-POPs). There are close correlations among these types of pollutants for their formation during industrial processes. This review focuses on the basic properties, emission characteristics, and formation mechanisms of UP-POPs during industrial processes. The sources and emission levels of UP-POPs on global or regional scales are also summarized. Finally, the progress in the studies associated with the emission characteristics and emission factors of UP-POPs from Chinese industries are reviewed.