From the July, 1 2013 Congressional Research Service report: Syria’s Chemical Weapons:
Issues for Congress:
The use or loss of control of chemical weapons stocks in Syria could have unpredictable consequences for the Syrian population and neighboring countries as well as U.S. allies and forces in the region. Congress may wish to assess the Administration’s plans to respond to possible scenarios involving the use, change of hands, or loss of control of Syrian chemical weapons.
Syria has produced, stored, and weaponized chemical weapons, but it remains dependent on foreign suppliers for chemical precursors. The regime of President Bashar al Asad reportedly has stocks of nerve (sarin, VX) and blister (mustard gas) agents, possibly weaponized into bombs, shells, and missiles, and associated production facilities. Chemical weapons and their agents can deteriorate depending on age and quality. Little is known from open sources about the current size and condition of the stockpile. Syria continues to attempt to procure new supplies of chemical weapons precursors, which are dual-use, through front companies in third countries. Most countries that have had chemical weapons arsenals in the past have destroyed these weapons under the Chemical Weapons Convention, or are in the process of destroying them. The U.S. intelligence community cites Iran, North Korea, and Syria as having active chemical weapons programs.