Ten things about the Chemical Weapons Convention

The 16-year-old Chemical Weapons Convention has been in the spotlight since Syria decided to join in an apparent bid to avoid US-led military intervention over the government's alleged use of chemical weapons. But here are some lesser known facts about the origins of the treaty, whom it covers, what it covers - and who has complied with its obligations.

1. Modern use of chemical weapons dates back to World War I, when weaponised commercial chemicals such as chlorine, phosgene and mustard gas caused agonising suffering and tens of thousands of deaths. The development and stockpiling of chemical weapons accelerated during the Cold War, though their actual use was recorded only in a few cases

2. A ban was first floated in 1968, but the text for the convention was only submitted to the UN General Assembly for approval 24 years later

3. Between April 1997, when the convention came into force, and July 2013, the Organisation for the Prohibition of Chemical Weapons (OPCW) - which polices the convention - conducted more than 5,000 inspections in 86 out of the 189 countries that are party to the convention. But the OPCW can't do much to enforce compliance, outside recommending measures to states or referring matters to the UN General Assembly or Security Council

4. Seven state parties have declared chemical weapons stockpiles totalling over 70,000 tonnes, and so far some 80% of this has been destroyed

5. But only three countries - Albania, India and a third party widely believed to be South Korea - have destroyed all their stockpiles

6. The countries with the biggest declared stockpiles, the United States and Russia, failed to meet deadlines for their total destruction in April 2007 and April 2012. The deadlines have now been extended once again

7. The US currently has a stockpile of some 3,000 tonnes of chemical agents - three times the amount Western powers say Syria possesses

8. There are some contentious exclusions from the CWC, such as white phosphorus - which if used as smoke (to camouflage movement) is not considered a chemical weapon despite its potential toxic effects. Napalm and dynamite are excluded because their primary destructive effects are considered to be incendiary and not chemical

9. The CWC's remit also does not include biological weapons - weaponisable bio-agents such as bacteria, viruses or fungi - which is covered by the Biological Weapons Convention

10. Five states - Angola, North Korea, Egypt, South Sudan and Syria - have neither signed nor ratified the agreement, though Syria is now in the process of doing so. Israel and Burma (also known as Myanmar) have signed but not ratified.