Ricin is a highly toxic protein that is derived from the bean of the castor plant ( Ricinus communis ). The toxin causes cell death by inactivating ribosomes, which are responsible for protein synthesis. Ricin can be produced in liquid, crystal or powdered forms, and it can be inhaled, ingested, or injected. It causes fever, cough, weakness, abdominal pain, vomiting, diarrhea, dehydration, and death. There is no cure for Ricin poisoning, and medical treatment is simply supportive.

Chemical structure and pathological pathway. Ricin is a protein composed of two hemagglutinins and two toxins (RCL III and RCL IV). The toxins are made up of an A polypeptide chain and a B polypeptide chain, which are joined by a disulfide bond. The general molecular structure of Ricin is similar to other biologically produced toxins, such as botulinum, cholera, diptheria, and tetanus.

The B portion of Ricin binds to glycoproteins and glycolipids that terminate with galactose on the exterior of cell membranes. Ricin is then transported inside the cell by endocytosis. Once inside the cytosol of the cell, the A portion of the molecule binds to the 60S ribosome, stopping protein synthesis. A single molecule of Ricin can kill a cell.

Ricin poisoning. Ricin poisoning can occur by dermal (skin) exposure, aerosol inhalation, ingestion, or injections, and the symptoms vary depending on the route of exposure. If Ricin comes in contact with the skin, it is unlikely to be fatal, unless combined with a solvent such as DMSO. Aerosol inhalation of Ricin can cause symptoms within four to eight hours. Fever, chest tightness, cough, nausea, and joint pain may occur. Ricin can cause cell death in the respiratory system and eventual respiratory failure. If Ricin is ingested, it can cause severe lesions in the digestive system within two hours of exposure. It may cause abdominal pain, nausea, vomiting, and bloody diarrhea. Eventual complications include cell death in the liver, kidney, adrenal glands, and central nervous system. Injection of Ricin causes local cell death in muscles, tissue, and lymph nodes. Ricin poisoning causes death generally within three to five days. If Ricin exposure does not cause death within five days, the victim will probably survive.

There is no cure for Ricin poisoning, although a vaccine is currently under development. Treatment for dermal exposure includes decontamination using soap and water or a hypochlorite (bleach) solution, which deactivates Ricin. In case of aerosol inhalation, treatment is the administration of oxygen, intubation, and ventilation. Ingestion of Ricin is treated with activated charcoal.

Ricin production and use as a biological weapon. Ricin comes from castor beans, which produce castor oil, a component of brake fluid and hydraulic fluid. One million tons of castor beans are processed each year and the resulting waste mash contains 5–10% Ricin. The 66,000 Dalton protein can be purified from the mash using chromatography. Once purified, Ricin is a very stable molecule that is able to withstand changes in environmental conditions.

Ricin is considered moderately threatening as a biological warfare agent. Although it is environmentally stable, relatively easy to obtain, highly toxic, and has no vaccine, it is not communicable like other biological agents such as anthrax and smallpox. Ricin is most often considered a threat as a food or water contaminant. A large amount would be required to cover a significant area.

The most famous case involving Ricin is the assassination of the Bulgarian dissident Georgi Markov. In 1978, Markov was working in London as a British Broadcasting Company (BBC) correspondent. As he was walking across Waterloo Bridge, a man jabbed the tip of an umbrella into Markov's right thigh, murmured an apology, and slipped away into the crowd. Markov died four days later. After the collapse of the Soviet Union, the new Bulgarian government admitted that their Secret Service had been responsible for the murder. The KGB produced the murder weapon: an umbrella modified to inject a 1.7 mm platinum pellet filled with Ricin into Markov's leg.

Incidents involving Ricin have occurred in the United States. Four men were convicted of plotting to kill a United States marshal with Ricin in Minnesota in 1991. They were all members of an extremist antigovernment group called the Patriots Council. In 1995, Canadian officials stopped Thomas Lavey at the border with Alaska with a bag of Ricin. He was also in possession of guns, ammunition, manuals for making biological and chemical weapons, and neo-Nazi literature.

Ricin has been loosely linked to the al-Qaeda terrorism network. In January 2002, police in London were advised that of a group of men were manufacturing Ricin in their apartment. Although only a small amount of Ricin was found, castor beans as well as equipment for crushing and extracting Ricin from the beans were discovered. Seven men of North African background were arrested in the incident, and security experts speculate that they had links to al-Qaeda. There also are reports that Ricin was found in caves abandoned by the Taliban in Afghanistan.



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Animal Science at Cornell University. "Ricin Toxin From Castor Bean Plant." < http://www.ansi.cornell.edu/plants/toxicagents/Ricin/Ricin.htm > (February 5, 2003).

BBC News UK "Seventh Arrest in Ricin Case." < http://news.bbc.co.uk/1/hi/uk/2637515.stm > (February 5, 2003).

Medical NBC Online. "Ricin." < http://www.nbc-med.org/SiteContent/RedRef/OnlineRef/FieldManuals/medman/ icin.htm > (February 5, 2003).

Mirarchi, Ferdinando L., eMedicine. "Ricin." < http://www.emedicine.com/emerg/topic889.htm > (February 5, 2003).


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