Last week, the Syrian government was accused of using chemical weapons in an attack that killed 1,429 people in Damascus. Here are 9 things you should know about chemical weapons.

1. The general and traditional definition of a chemical weapon is a toxic chemical contained in a delivery system, such as a bomb or shell. The Chemical Weapons Convention (the international treaty that bans chemical weapons) applies the term to any toxic chemical or its precursor that can cause death, injury, temporary incapacitation or sensory irritation through its chemical action.

2. The toxic chemicals that have been used as chemical weapons, or have been developed for use as chemical weapons, can be categorized as choking, blister, blood, or nerve agents. The most well known agents are choking agents—chlorine and phosgene; blister agents—mustard and lewisite; and blood agents—hydrogen cyanide, and nerve agents—sarin, tabun, VX.

3. It is believed that Syria is able to develop and produce the blistering agent, mustard gas, as well as the nerve gas sarin—and possibly also VX nerve agent.  Nerve agents are called that because they attack the human nervous system.

4. A lethal dose (2 teaspoons) of VX, absorbed through the skin, can kill within minutes. A lethal dose (0.06 ounces) of sarin, absorbed through the skin, can kill within 5-10 minutes. A lethal dose (.14 ounces) of tabun, absorbed through the skin, can kill within 15-20 minutes.

5. Sarin is a nerve agent first developed by German researchers in the late 1930s. Up to 500 times more toxic than cyanide, it is a colorless and odorless liquid that causes severe muscle spasms, vision loss, and asphyxia, and which can kill within a minute of contact in extreme cases. The best-known recent use of sarin previously was in the 1995 Tokyo subway attack in which members of a domestic cult-turned-terrorist group punctured bags of liquid sarin with sharpened umbrella tips in subway cars. At least 13 people died in the attack and some 1,000 were injured. Iraq's Saddam Hussein also used sarin against Iranian forces in the Iran-Iraq war, and in 1988 as part of the cocktail of chemical weapons he unleashed against the Kurdish population of Halabja in northern Iraq. Sarin was classified as a “weapon of mass destruction” and banned in the United Nations' Chemical Weapons Convention of 1993.

6. Mustard gas is not a particularly effective killing agent (though in high enough doses it is fatal) but can be used to harass and disable the enemy and pollute the battlefield. Only four percent of combat deaths in World War I were caused by gas. In that war, the skin of victims of mustard gas blistered, their eyes became very sore and they began to vomit. Mustard gas caused extremely painful internal and external bleeding and attacked the bronchial tubes, stripping off the mucous membrane. Fatally injured victims sometimes took four or five weeks to die of mustard gas exposure.

7. During World War II, Japan was the only country to use chemical weapons on the battlefield. Adolf Hitler refrained from the use of chemical weapons in war, though not from the use of poison gases in concentration camps, likely because of fear of reprisals in kind. During the Cold War, the United States and the Soviet Union both maintained enormous stockpiles of chemical weapons, amounting to tens of thousands of tons. The amount of chemical weapons held by these two countries was enough to destroy much of the human and animal life on Earth.

8. As of February 2013, 78.57%, of the world's declared stockpile of 71,196 metric tons of chemical agent have been verifiably destroyed. Iraq, the Libyan Arab Jamahiriya, the Russian Federation, and the United States all have declared they have remaining stockpiles. Combined they must destroy 8.67 million items, including munitions and containers containing in total, 71,196 metric tons of extremely toxic chemical agents. By comparison, a tiny drop of a nerve agent, no larger than the head of a pin, can kill an adult human being within minutes after exposure.

9. Over 98% of the world's population lives within territories where the Chemical Weapons Ban has become the law of the land. The two states that have signed the treaty but have not yet ratified it are Israel and Myanmar. The five states that have neither signed nor acceded to the Chemical Weapons Convention are Angola, Egypt, North Korea, South Sudan, and Syria.


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