Ricin
Ricin is a highly toxic protein derived from the castor bean plant, scientifically known as Ricinus communis. This potent toxin poses significant concerns for national security and law enforcement due to its potential use in terrorist attacks, particularly since there is currently no antidote available for ricin poisoning. The extraction process of ricin occurs as a byproduct of castor oil production, with over a million tons of castor beans processed annually. Ricin is notably dangerous in aerosolized form, which could disperse the toxin over a wide area. Symptoms of ricin poisoning manifest differently depending on the method of exposure, whether inhaled or ingested, leading to severe health complications and potentially death within 36 to 72 hours. Historical instances of ricin being used as a weapon include the assassination of Bulgarian dissident Georgi Markov in 1978, and various domestic cases in the United States have highlighted its accessibility. Forensic detection techniques for ricin include immunochromatographic devices and laboratory assays that help quantify its presence.
Ricin
DEFINITION: Poisonous protein extracted from beans of the plant with the botanical name Ricinus communis and the common name castor bean.
SIGNIFICANCE: Given that the plant source for the highly toxic substance ricin is easy to obtain, concerns have arisen among law-enforcement and national security agencies that terrorists might attempt to use this toxin in attacks. Such fears are exacerbated by the fact that no antidote to ricin poisoning has been developed.
More than one million tons of castor beans are processed every year for their oil, and the poison ricin can be prepared from the waste created in this processing. Near the end of World War I, the US Chemical Warfare Service extracted ricin from castor beans as part of a plan to produce a toxic weapon. The possession of ricin is illegal in the United States; ricin is listed as a restricted substance (select agent) in the U.S. Biological Weapons Anti-Terrorism Act of 1989.
Preparations of ricin generally appear as gray, off-white, or white powders. Ricin is a heat-resistant protein that consists of two protein subunits, an A chain and a B chain. The B chain is a lectin (carbohydrate-binding protein) and enables ricin binding and internalization by cells; the A chain is the lethal component. To be toxic, ricin has to enter cells, where the A chain enzymatically inactivates ribosomes, the protein-synthesizing machines of cells. The toxic dose of ricin for humans is approximately 500 micrograms; ricin is more toxic on a weight basis than most common nerve gases or chemical weapons. Ricin would be most dangerous as a weapon of in aerosolized form—that is, in the form of a fine powder that does not clump—as this form would enable the dispersion of the substance over a wide area.
Signs and Symptoms of Ricin Poisoning
The effects of ricin vary depending on how the poison enters the body. If ricin is inhaled, symptoms usually appear within a few hours to eight hours. These include difficulty breathing, fever, cough, nausea, profuse sweating, accumulation of fluid in the lungs, low blood pressure, and respiratory failure. If ricin is ingested with food or liquids, symptoms usually appear in less than six hours and include diarrhea, vomiting, severe dehydration, hallucinations, blood in urine, and seizures. Over the course of several days, liver, kidney, and spleen failure may result.
Time to death from ricin exposure depends on the dose and method of exposure; death may take place from thirty-six to seventy-two hours after initial exposure. Victims who survive past seventy-two hours often recover. Treatment consists of supportive care based on the route of entry of the ricin; for example, for ingested ricin, activated charcoal is administered orally. Other therapy includes provision of intravenous fluids, help in breathing, and medications for low blood pressure and seizures.
Criminal Cases Involving Ricin
Perhaps the most famous case of the use of ricin as a weapon is that of the assassination of Bulgarian dissident and exile Georgi Markov in London in 1978. Markov was a writer who worked for various Western European radio stations and was a persistent critic of the communist Bulgarian government. Agents of the Bulgarian government made three attempts on his life, and the third was successful. At a bus stop, Markov was reportedly stabbed in the thigh with an umbrella that had been specially fabricated to inject a small metal pellet that was designed to release ricin. He died a few days later. Because of Markov’s verbalized suspicions about the incident, an was requested by Scotland Yard. The examination recovered a small metal sphere the size of a pinhead from Markov’s body. The artifact, which was composed of expensive and finely machined metals, contained traces of ricin in an inner chamber.
Less than two weeks before the attack on Markov, another Bulgarian dissident, Vladimir Kostov, was shot in Paris with a bullet carrying the same kind of pellet that killed Markov. The attempt on Kostov failed because the pellet did not lodge deeply in his body and was removed before it could deliver a lethal dose of ricin. The crimes against Markov and Kostov remain unsolved technically, but KGB defectors claimed that the KGB provided technical assistance to the perpetrators. In the twenty-first century, a journalist followed the trail of Markov's assassin, identifying him as an Italian criminal working for the KGB.
In 1994 and 1995, members of a domestic American terrorist group, the Minnesota Patriots Council, were convicted of possession of ricin and of conspiring to kill law-enforcement officers. They had responded to an advertisement in a radical right-wing magazine offering the materials necessary to make ricin and instructions on how to make the toxin.
In February 2004, ricin was detected in materials in the Washington, DC, mail office of US Senate Majority Leader Bill Frist. Three buildings were closed while investigations and tests for contamination were completed, and no human poisonings occurred. The case remains unsolved. Other cases involving small amounts of apparently homemade ricin made the news in the United States in 2006 and 2008, illustrating the relative ease with which this substance can be produced.
Forensic Detection of Ricin
Forensic techniques for the detection of ricin include the use of lateral-flow immunochromatographic devices for on-site detection as well as enzyme-linked immunosorbent assays in the laboratory. Other methods that have been employed for ricin detection and quantification, as it is a protein, include conventional amino acid sequencing and extremely sensitive and specific techniques.
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