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Ricin has an average lethal dose in humans of 0.2 milligrams (1/5,000th of a gram), though some sources give higher figures.
Additional recommended knowledge
Ricin is poisonous if inhaled, injected, or ingested, acting as a toxin by the inhibition of protein synthesis. Ricin is 6000 times more toxic than cyanide and 12000 times more poisonous than rattlesnake venom by weight. While there is no known antidote, the US military has developed a vaccine. Symptomatic and supportive treatment is available. Long term organ damage is likely in survivors. Ricin causes severe diarrhea and victims can die of shock. (See abrin).
Deaths caused by ingestion of seeds are rare. Eight beans are considered toxic for an adult. A solution of saline and glucose has been used to treat ricin overdose.  The case experience is not as negative as popular perception would indicate.
Many plants such as barley have the A chain but not the B chain. Since people do not get sick from eating large amounts of such products, ricin A is of extremely low toxicity as long as the B chain is not present.
Ricin is easily purified from castor-oil manufacturing waste. The seed-pulp left over from pressing for castor oil contains on average about 5% by weight of ricin. Since 0.2 mg of purified Ricin constitutes a fatal dose, this is a considerable amount of ricin.
In the United States, a person caught manufacturing or possessing ricin may be sentenced to up to 10 years for possession or life for possession with intent to provide to a foreign government or use as a weapon. (18 USC 175) 
Potential medicinal use
Ricins may have therapeutic use in the treatment of cancer. Ricin could be linked to a monoclonal antibody to target malignant cells recognized by the antibody. Genetic modification of ricin is believed to be possible to lessen its toxicity to humans, but not to the cancer cells. A promising approach is also to use the non-toxic B subunit as a vehicle for delivering antigens into cells thus greatly increasing their immunogenicity. Use of ricin as an adjuvant has potential implications for developing mucosal vaccines.
Therapeutically, ricin is used in magic bullets to specifically target and destroy cancer cells.
Use as a chemical/biological warfare agent
The United States investigated ricin for its military potential during the First World War. At that time it was being considered for use either as a toxic dust or as a coating for bullets and shrapnel. The dust cloud concept could not be adequately developed, and the coated bullet/shrapnel concept would violate the Hague Convention of 1899. The War ended before it was weaponized.
During the Second World War the United States and Canada undertook studying ricin in cluster bombs. Though there were plans for mass production and several field trials with different bomblet concepts, the end conclusion was that it was no more economical than using phosgene. This conclusion was based on comparison of the final weapons rather than ricin's toxicity (LD50 <30 mg.min.m–3). Ricin was given the military symbol W.
The best-known documented use of ricin as an agent of biological warfare was by the Soviet Union's KGB during the Cold War. In 1978, the Bulgarian dissident Georgi Markov was assassinated by Bulgarian secret police who surreptitiously 'shot' him on a London street with a modified umbrella using compressed gas to fire a tiny pellet contaminated with ricin into his leg. He died in a hospital a few days later; the body of Georgi Markov was passed to a special poison branch of the British MOD who discovered the pellet during an autopsy. The main suspect was the Bulgarian secret police; this was because Georgi Markov had defected from Bulgaria several years prior to the incident and was wanted for writing many controversial books on the communist government at the time, however, it was believed at the time that Bulgaria would not have been able to produce the poison, and it was also believed that the KGB had supplied it. The KGB denied any involvement although high-profile KGB defectors Oleg Kalugin and Oleg Gordievsky have since confirmed the KGB's involvement. Earlier, Soviet dissident Aleksandr Solzhenitsyn also suffered (but survived) ricin-like symptoms after a 1971 encounter with KGB agents.
Despite ricin's extreme toxicity and utility as an agent of chemical/biological warfare, it is extremely difficult to limit the production of the toxin. Under both the 1972 Biological Weapons Convention and the 1997 Chemical Weapons Convention, ricin is listed as a schedule 1 controlled substance. Despite this, more than 1 million metric tonnes of castor beans are processed each year, and approximately 5% of the total is rendered into a waste containing high concentrations of ricin toxin.
In August of 2002, US officials asserted that the Islamic militant group Ansar al-Islam tested ricin, along with other chemical and biological agents, in northern Iraq.
To put ricin used as weapon into perspective, it is worth noting that as a biological weapon or chemical weapon, ricin may not be considered very powerful if only in comparison with other agents such as botulinum or anthrax. Hence, a military willing to use biological weapons and having advanced resources would rather use either of the latter instead. Ricin is easy to produce, but is not as practical nor likely to cause as high casualties as other agents. Ricin is inactivated (ie, the protein changes structure and becomes less dangerous) much more readily than anthrax spores, which may remain lethal for decades. (Jan van Aken, an expert on biological weapons explained in an interview with the German magazine Der Spiegel that he judges it rather reassuring that Al Qaeda experimented with ricin as it suggests their inability to produce botulin or anthrax.)
The major reason it is dangerous is that there is no specific antidote, and that it is very easy to obtain (the castor bean plant is a common ornamental, and can be grown at home without any special care). Ricin is actually several orders of magnitude less toxic than botulinum or tetanus toxin, but those are more difficult to obtain.
Patented extraction process
The process for creating ricin is well-known, and for example described in a patent. The described extraction method is very similar to the preparation of soy protein isolates.
The patent was removed from the United States Patent and Trademark Office (USPTO) database sometime in 2004, but is still available online through international patent databases. Modern theories of protein chemistry cast doubt on the effectiveness of the methods disclosed in the patent.
Detected ricin incidents
Assassination of Bulgarian Dissident Georgi Markov, London 1978
On September 7, 1978 the Bulgarian dissident Georgi Markov was shot in the leg in public on Waterloo Bridge in the middle of London by a man using a weapon built into an umbrella. The weapon embedded a small pellet in Markov's leg which contained ricin. Markov died four days later.
Related arrests in Britain in 2003
On 5 January, 2003 the Metropolitan Police raided a flat in north London and arrested six Algerian men whom they claimed were manufacturing ricin as part of a plot for a poison attack on the London Underground. No ricin was recovered as a result of this raid.
In South Carolina
In 2003, a package and letter sealed in a ricin-contaminated envelope was intercepted in Greenville, South Carolina, at a United States Postal Service processing center.
In Washington, D.C. in 2003
Ricin was detected in the mail at the White House in Washington, D.C. in November of 2003. The letter containing it was intercepted at a mail handling facility off the grounds of the White House, and it never reached its intended destination. The letter contained a fine powdery substance that later tested positive for ricin. Investigators said it was low potency and was not considered a health risk. This information was not made public until February 3, 2004, when preliminary tests showed the presence of ricin in an office mailroom of U.S. Senate Majority Leader Bill Frist's office. There were no signs that anyone who was near the contaminated area developed any medical problems. Several Senate office buildings were closed as a precaution.
In Richmond, VA
In January 2006, ricin was found in a home in the suburbs of Richmond, VA. It was in the form of mashed castor beans. Although the suspect, Chetanand Sewraz, was allegedly isolating the toxin to kill his estranged wife, and not for some form of bioterrorism, it nonetheless highlighted the ease with which ricin toxin can be made.
In Austin, Texas
On 23 February 2006, a student in the Moore-Hill dormitory at the University of Texas at Austin found a strange powder in a roll of quarters she was using to do laundry. The University Environmental Health and Safety department immediately sanitized the affected rooms. Lab results (returned the following Friday) indicated ricin. The source of the powder remains unknown, with both the university and Joint Terrorism Task Force investigating. The student and her roommate were being treated for potential exposure to the poison, although neither has exhibited symptoms. After cleansing and reinspection of the affected rooms (completed at 2:30am), the dorm reopened. News reports on 25 February report that further testing has indicated that the substance found is not, in fact, ricin. The identity of the powder has yet to be determined.
Notes and references
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ricin". A list of authors is available in Wikipedia.|