This report details the technical background to the GlobalMercury Assessment 2013 Sources, Emissions, Releases andEnvironmental Transport (summary for policy-makers)that has been developed in response to Decision 25/5 III,paragraph 36 of the Governing Council of the UnitedNations Environment Programme (UNEP), that: Requestthe Executive Director, in consultation with Governments,to update the 2008 report entitled Global AtmosphericMercury Assessment: Sources, Emissions and Transport forconsideration by the Governing Council / Global MinisterialEnvironment Forum at its twenty-seventh session.