Illustration showing burning of penis and scrotum of a soldier exposed to mustard gas whilst sitting on the ground during the First World War. Mustard gas was used as a chemical warfare agent in the First world War. Exposure to mustard gas, a chemical warfare agent, can cause blistering of the skin and mucous membrane on contact. Mustard gas can also cause coughing and shortness of breath in the short term. It also has long term effects such as mouth, throat and skin cancer as well as leukaemia. Published in An Atlas of Gas Poisoning, 1918.