Definicija: PCDD are formed (along with variants including furans) when compounds containing chlorine are burnt at low temperature in improperly operated/designed domestic refuse and industrial waste incinerators where PCDDs can be found in both the flue gases and the fly ash.

Definicija: PCDD nastane (poleg različic s furani), ko so klorove spojine na nizki temperaturi sežgane v nepravilno delujočem oziroma nepravilno oblikovanem domačem odlagališču odpadkov ali v industrijski sežigalnici odpadkov. PCDD-ji so prisotni v izpušnih plinih in elektrofilterskem pepelu.