One category of weapons of mass destruction, chemical weapons were used in World War I and by several military forces later, despite international conventions to ban them. They include poisonous gases, such as chlorine, mustard gas, phosgene, and sarin, and food contaminants, such as ricin and botulinus toxin, that are deliberately introduced into foodstuffs, such as flour, with the intention of harming people. The definition is broadened to include substances such as napalm, the modern and far more deadly equivalent of burning sulfur and pitch that were used in some ancient wars. Some chemical weapons, e.g., sarin gas, have been used in terrorist attacks in recent years.
Subjects: Public Health and Epidemiology.