The Kyiv Protocol on Pollutant Release and Transfer Registers (PRTRs) was adopted on 21 May 2003 and entered into force on 8 October 2009. It is the only legally binding international instrument on pollutant release and transfer registers. Its objective is "to enhance public access to information through the establishment of coherent, nationwide pollutant release and transfer registers (PRTRs)."
PRTRs are inventories of pollution from industrial sites and other sources. Although regulating information on pollution, rather than pollution directly, the Protocol is expected to exert a significant downward pressure on levels of pollution, as no company will want to be identified as among the biggest polluters. All UN Member States can join the Protocol, including those which have not ratified the Aarhus Convention and those which are not members of the United Nations Economic Commission for Europe. It is by design an 'open' global treaty.