× Information on this section of ECOLEX comes from the InforMEA Portal which compiled information from MEA Secretariats with the support of the European Union. The accuracy of the information displayed is the responsibility of the originating data source. In case of discrepancy the information as displayed on the respective MEA website prevails. Decision II/4: Isomers Document type Decision Reference number II/4 Date Jun 27, 1990 SourceUNEP, InforMEA Status Active Subject Waste & hazardous substances, Air & atmosphere Treaty Montreal Protocol on Substances that Deplete the Ozone Layer (Sep 16, 1987) Meeting Website ozone.unep.org Abstract The Second Meeting of the Parties decided in Dec. II/4 to clarify the definition of “controlled substance” in paragraph 4 of Article 1 of the Protocol so that it is understood to include the isomers of such substances except as specified in the relevant Annex.