Chemical weapons

• GB, also known as sarin, is the nerve agent that killed 12 and injured 5,500 when cultists released the chemical in the Tokyo subway system in 1995. A deadly dose on the skin is 1,700 mg (about 0.06 of an ounce).

• VX, another nerve agent, is even more deadly, with a lethal skin dose estimated at 10 mg (0.00035 of an ounce, a tiny pinpoint).

• Mustard agent, also called blister agent, causes burning or blistering of the skin, lungs and mucus membranes. Used by both sides in World War I, it can blind or kill a victim. Often it causes tissue damage, with death resulting in a few days or weeks.