Ricin is a poison manufactured from the castor bean (Ricinus communis). It is considered to be twice as deadly as cobra venom. It can be inhaled, injected, or ingested. As a toxin it acts by the inhibition of protein synthesis. There is no known antidote. In small doses, ricin causes the human digestive tract to convulse (see castor oil). In large doses, ricin causes severe diarrhea and victims can die of shock.
In August of 2002, US officials said that the group Ansar al-Islam tested ricin, along with other chemical and biological agents, in northern Iraq.
The Bulgarian dissident Georgi Markov was assassinated by Bulgarian secret police in London using a modified umbrella which fired a platinum pellet containing ricin in London in 1978.
Traces of ricin were detected by British police in a flat in Wood Green, North London after a raid on a suspected ring of terrorists in January 2003.