Abstract
Chemical warfare means the use of chemical agents that have direct toxic effects on animals, plants and humans, as weapons. The first documented use of a chemical agent for warfare purposes occurred in ancient times around 10,000 BCE in South Africa when weapons were dipped in chemicals and then used to attack and defend from enemies. However, much of the evidence lacks detail to provide thorough accounts of such events. Nevertheless, we aimed to systematically gather the most comprehensive account of all publicly known incidents involving chemical weapons throughout history. We identified 121 instances of chemical weapon use between 10,000 BCE and October 2023 spanning 49 countries and causing at minimum 2,110,360 injuries and 2,930,769 deaths. Across the 121 incidents, at least 165 chemical agents were used. Of the known chemical agents, the top three were sulphur mustard (n = 16, 12.1%), hydrogen cyanide (n = 12, 7.3%) and chlorine gas (n = 11, 6.7%). Of the known chemical classes, the top three used were vesicants (blistering agents) (n = 31, 18.8%), choking (pulmonary) agents (n = 18, 10.9%) and nerve agents (n = 18, 10.9%). If a chemical agent was not reported, the chemical class was reported as unknown (n = 35, 21.2%). A small number of chemical weapons were used that fell outside of the main categories of agents (n = 20, 12.1%). Chemical weapons remain a serious concern locally and globally, and there are few data on the global epidemiology of such incidents. Prevention, early detection and rapid response are key and can be enabled by global surveillance for chemical incidents.