There have been numerous reports of chemical weapons attacks in the Syrian Civil War, beginning in 2012, and corroborated by national governments, the United Nations (UN), the Organisation for the Prohibition of Chemical Weapons (OPCW), Human Rights Watch (HRW), and media organizations. The attacks occurred in different areas of Syria, including Khan al-Assal, Jobar, Saraqib, Ashrafiyat Sahnaya, Kafr Zita, Talmenes, Sarmin and Douma. The deadliest attacks were the August 2013 sarin attack in Ghouta (killing between 281 and 1,729 people) and the April 2017 sarin attack in Khan Shaykhun (killing at least 89 people). The most common agent used is chlorine, with sarin and sulphur mustard also reported. Almost half of the attacks between 2014 and 2018 were delivered via aircraft and less than a quarter were delivered from the ground, with the remaining attacks having an undetermined method of delivery. According to a February 2019 study by researchers at the Berlin-based Global Public Policy Institute, chlorine was used in 91.5% of chemical attacks since 2012.