WHO: Environmental health. Questions and answers

http://www.who.int/environmental_health_emergencies/deliberate_events/chemical_release/en/

Q18: How can chemical weapons be disposed of or destroyed?

The Organization for the Prohibition of Chemical Weapons (OPCW) has the responsibility for overseeing and verifying the safe and secure destruction of these weapons in countries that are Parties to the Chemical Weapons Convention. A number of techniques, including incineration, exist for destroying chemical weapons but older methods such as dumping, burial, or open-pit burning are prohibited under the Chemical Weapons Convention.

UPDATE 14.1.2014 UK  supporting  economically the  neutralizations, hydrolysation etc of the  chemical  toxins

http://www.jpost.com/Breaking-News/UK-to-help-US-expedite-destruction-of-Syrian-chemical-arms-338034