6. Mustard gas is not a particularly effective killing agent 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.
