Toxins are any poisonous substances that can be produced by an animal, plant, or microbe. Because of their complexity, most toxins are difficult to synthesize in large quantities by traditional chemical means. However, they may be harvested from cultured sources or produced by genetically engineered microbes. Toxins are odorless, tasteless, and nonvolatile. Ricin (C16-A036) and saxitoxin (C16-A018) are the only toxins listed in the Chemical Weapons Convention (Schedule 1). Several countries have stockpiled a limited number of toxins. Their use on the battlefield

has been alleged (e.g., Laos, Kampuchea, and Afghanistan) but not documented to the extent that it is universally accepted. Toxins have been used for political assassinations (e.g., 1978 murder of Georgi Markov with ricin) and terrorists have threatened the use of toxins, usually through contamination of food or water supplies.