Mustard gas is a chemical weapon that is classified as a vesicant, meaning that it causes blisters and lesions on the skin and in the respiratory tract. This chemical weapon was infamously used during World War I, and this undoubtedly contributed to the decision to ban the use of such weapons in war in the Geneva Protocol of 1925. Also known as sulfur mustard or H, it is among the list in the Chemical Weapons Convention of 1993, which bans the production, use, sale, or stockpiling of such weapons.
Despite its name, this weapon is not a gas, but rather a very thick, volatile liquid. The plumes of it that wafted over the trenches of World War I were created by aerosolizing the liquid, typically by encasing it in fired projectiles. Once aerosolized, sulfur mustard can endure for several days in the water and soil it settles on.
Impure mustard gas smells a bit like mustard or onions, and it sometimes has a yellow appearance, which explains the common name. When purified, however, it is odorless and colorless, which can potentially be very dangerous, as symptoms of exposure typically take several hours to set in. When treatment is offered quickly, recovery is possible; after several hours of exposure, however, it can be difficult to reverse the effects of the chemical.
Exposure to mustard gas causes distinctive burns on the skin. Many victims of the gas in World War I were blinded or had severe vision damage as a result of their exposure, since the chemical is very hard on the mucus membranes. When inhaled, the resulting blister formation in the respiratory tract can lead to death, typically after hours of suffering. It is also known to be a mutugen and carcinogen, meaning that even after recovery, exposed victims could still experience health problems.
After suspected exposure to sulfur mustard, people should immediately discard the clothing they are wearing and bathe in clean water. There is no antidote, so washing it off the body as quickly as possible it vital to limit injury. After these basic first aid measures, prompt medical attention is necessary; at a hospital, medical professionals can help remove the chemical from the victim's system and treat the symptoms as they arise.