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Ricin is a highly toxin protein. It is a by-product of castor oil production. The U.S. military experimented with using ricin as a chemical warfare agent in the 1940s. There have been a few high profile cases of individuals poisoned with ricin, and ricin was possibly used as a warfare agent in the 1980s in Iraq.


Ricin's extreme potency allow it to be a potential terrorist or warfare agent.

Therapeutically, ricin has been used experimentally to specifically target and destroy cancer cells. Its unique intracellular trafficking properties may someday allow it to be developed as a vaccine vector.

Name: Ricin

Use: Chemical warfare, possible Cancer treatment

Source: By-product of castor oil production

Recommended daily intake: None

Lethal Dose: 5-10 µg/kg bodyweight

Absorption: Inhalation, ingestion, injection

Toxicity/symptoms: Depends on method of exposure

Regulatory facts:



Routes of Exposure

Accidental exposure is very rare, but could occur from ingesting castor beans or being exposed to certain aspects of castor oil production.

If refined, it could be used as a chemical warfare agent. Exposure could occur on the battlefield or to civilians through terrorism. Ricin could be transmitted to people through air, food, or water.

In 1978, Georgi Markov, a Bulgarian activist living in London, died after being poisoned with ricin. He was attacked with an umbrella that was prepared with a ricin pellet, which was propelled under Markov's skin.

Mechanism of Toxicity

Ricin disrupts protein synthesis by attacking the ribosome. Incredibly small amounts of ricin reaching the cytosol of a cell can be fatal to the cell because of inhibited protein synthesis.

Signs and Symptoms of Ricin Exposure

Symptoms of ricin exposure vary by route of exposure.

Symptoms of ricin ingestion:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Severe dehydration
  • Kidney and liver symptoms

Symptoms of ricin inhalation:

  • Breathing difficulties
  • Shortness of breath
  • Chest tightness and coughing
  • Pulmonary edema
  • Respiratory failure


There is no antitoxin available for ricin. Ricin poisoning is therefore only treated through supportive care. Supportive care will vary based on the route of exposure, degree of exposure, and length of time following poisoning.


CDC. 2008. Ricin. Accessed 5/6/2008.

Lord MJ, Jolliffe NA et al. 2003. Ricin: Mechanisms of cytotoxicity. Toxicol Rev. 22(1):53-64.

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