CDI Factsheet: Ricin

Ricin is the third most toxic substance known after plutonium and botulism. Its recent discovery at a Wood Green flat in London marks the first 'specific threat' in the United Kingdom linked to Muslim extremists since Sept. 11, 2002. Ricin's potential as a powerful terrorist weapon is high, as it is relatively easy to produce and has no antidote. Indeed, it takes so little ricin to kill one human being that its use can be undetectable. It also offers a method to instigate panic and disorder as a "disabling agent" if used to pollute water and food supplies.

 
Background

Ricin works by blocking protein synthesis at the cellular level. It was discovered in 1800 by Hermann Stillmark, who uncovered the properties of lectins, a type of versatile plant protein. While extracting oil from castor beans, he discovered ricin, the toxic protein making up 1 percent to 5 percent of the beans' weight. Paul Erlich worked with the lectins ricin and abrin in the 1890s, forming the basis for the study of immunology. Ricin was also studied in the 1950s for use in fighting cancer. It is because of ricin's high levels of toxicity and ease of use that the U.S. and British governments jointly undertook to produce a W (named for ricin, compound W) bomb during WWII.

 
How can it potentially be used, and what are its symptoms?

Ricin can be delivered to the human body via ingestion, injection, or inhalation. Dermal, or physical contact, while not recommended, poses little danger due to negligible absorption.

 
Ingestion

Ricin is less toxic when introduced orally, because the chance for absorption is poorer as it travels through the digestive tract. This has been studied in relation to beans, seeds, and ricin itself. The LD 50 percent (or lethal dose responsible for killing 50 percent of the test population) is 30 mcg/kg. The fatality rates for ingestion of castor beans and seeds, as indicated by past studies are quite low ranging from 1.9 percent and 6 percent.

The symptoms resulting from ricin ingestion occur within a few hours. These include abdominal pain, vomiting, and diarrhea (which is sometimes bloody). Within several days victims will experience severe dehydration, decreased urination, and lowered blood pressure, although, according to one estimate by Cornell University, if death has not occurred within three to five days, the victim will usually recover.

Typically, serious oral ricin poisoning causes gastroenteritis, gastrointestinal hemorrhage, and hepatic, splenic, and renal necrosis. Death is usually onset by a shutdown of the circulatory system. While less deadly than if injected or inhaled, the dangers of food and water contamination are severe, and could well represent the most potent terrorist use of the toxin, serving as a means to foment mass hysteria.

 
Injection

Ricin has achieved a certain amount of notoriety in the past 30 years, due in large part to its use in the suspected 1978 KGB assassination of Bulgarian defector and BBC World Service commentator, Georgi Markov, in London. In a fashion more befitting a Hollywood spy movie, a poison pellet containing an estimated 0.28 milligrams of ricin was stabbed into his thigh with the tip of an umbrella. Three days later he died of cardiac failure, having been afflicted with a host of other ailments. Although no ricin was found, it was suspected by the doctor, who recreated the scenario, injecting a laboratory pig, which later died, in a similar fashion, and with similar symptoms. The LD50 for ricin through parenteral exposure (or being taken into the body or administered in a manner other than through the digestive tract — such as by intravenous or intramuscular injection) — 3 micrograms — is capable of 'severe local lymphoid necrosis, gastrointestinal hemorrhage, liver necrosis, diffuse nephritis, and diffuse splenitis.

 
Inhalation

In 1995, members of the Minnesota Patriots Council, an extremist American anti-government organization, were arrested for plotting the murder of a U.S. marshal using ricin. They had planned on sprinkling the substance on the door handles of the marshal's vehicle as well as the car heater fan. The incident illustrates the potential common danger even a small and relatively unsophisticated organization can wreak. Indeed, had those who carried out the 1995 sarin attack on the Tokyo subways used ricin — which is far deadlier and easier to produce — the results could have been catastrophic.

Airborne and inhaled, ricin becomes exponentially more dangerous than if simply touching the skin. While there have been no studies on human beings; it was shown with rats that the airborne ricin actually binds to ciliated bronchial lining cells, alveolar macrophages, and alveolar lining cells within the lungs.

It is estimated that the LD50 dose would be similar to that for injection. In other words, three micrograms would cause weakness and major symptoms within 18-24 hours, followed by death within 36-72 hours. In studies performed with monkeys, death was preceded by flooding and inflammation of the lungs and air ways, diffuse necrosis, fibrinopurulent pneumonia, acute tracheitis, purulent mediastinal lymphadenitis, and adrenalitis.

 
Is there a cure?

No. However, it is possible to be immunized. The U.S. Army has begun licensing a new vaccine.

 
Conclusions

Ricin's dangers do not lie in its ability to cause mass death, but in its ease of production by unskilled individuals using readily available laboratory equipment. The primary ingredient — castor beans — can be obtained easily and cheaply, while directions for producing the poison can be readily found on the Internet.

The recent arrests in London indicate that international terrorists may have succeeded in producing ricin. It has been reported that at least one of the seven men arrested at the initial raid in Wood Green attended an al Qaeda training camp in Afghanistan. While ricin is categorized as posing a B (or 'moderate') threat by the Centers for Disease Control, the opportunities to create havoc and hysteria with it abound — especially through mass or even selective poisoning of food and water supplies. Moreover, with the high number of dangerous agents available in the terrorists' arsenal, vaccinating the general public, which in the case of ricin is the only protection, is fraught with difficulty.

Sources:

Franz, David R., and Jaax, Nancy K., 'Medical Aspects of Chemical and Biological Warfare, Chapter: 32 Ricin Toxin,' Falls Church, VA: Office of the Surgeon General. 1997.

Gardner, Frank, 'Ricin Find "Very Significant,"' BBC News World Edition, Jan. 8, 2003.

Hoffman, Bruce, Inside Terrorism, New York: Columbia University Press, 1998. pp. 201-2.

Mirarchi, Fernando L., and Allswede, Michael, 'CBRNE - Ricin,' emedicine, 2003.

Mostyn, Richard, 'Stopped at border, man carried lethal toxin,' Yukon News, Feb. 23, 1996.

Norton-Taylor, Richard, Hopkins, Nick, and Henley, Jon, 'Poison Suspect Trained at al Qaeda camp,' Guardian Unlimited, Jan. 10, 2003.

'Research Activities,' Universidade Nova de Lisboa Instituto Technologia Quimica e Biologica, available at: http://www.itqb.unl.pt/Research/Research_Divisions/Biology/Ricardo_Ferreira/Activities

'Ricin and the Umbrella Murder,' CNN.com/World, Jan. 8, 2003

'Ricin as a Weapon,' CNN.com/World, Jan. 8, 2003

'Ricin Toxin From Castor Bean Plant: Ricinus Communis, 'Cornell University Poisonous Plants Informational Database, online at: http://www.ansci.cornell.edu/plants/toxicagents/ricin/ricin.html

'Statement for the Record of Robert M. Burnham, Chief, Domestic Terrorism Section Federal Bureau of Investigation on Bioterrorism in America Before the United States House of Representatives Subcommittee on Oversight and Investigations,' Congressional Statement, Federal Bureau of Investigation, May 20, 1999

'Terror Police Find Deadly Poison,' BBC News World Edition, Jan. 7, 2003.

David Savino CDI Research Assistant dsavino@cdi.org

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