TOXIC WEAPONS : Why is Syria a concern? / International Institute for Strategic Studies (IISS)

Syria has the largest CW arsenal in the Middle East and likely the fourth-largest in the world (after the United States, Russia and North Korea). Its exact size is unknown, but it has been assessed that Syria has developed and stockpiled hundreds of tonnes of chemical weapons.

Syria is known to have developed
mustard gas, a blistering agent, and sarin, a nerve agent. It has also allegedly developed VX, a more powerful nerve agent, which lingers longer in the environment thereby increasing exposure rates, as well as cyanide gas. Chlorine is not thought to have figured in its arsenal, and would make little sense given its ineffectiveness as a chemical warfare agent. Its chemical agents have been weaponised into artillery shells, bombs and missiles, such as the Scud-B and -C missiles it acquired from North Korea from the 1990s onwards.