Science Fair Project Encyclopedia
The protein ricin (pronounced rye-sin) is a poison manufactured from the castor bean (Ricinus communis). Its name comes from the seed's resemblance to the tick. Ricin can be extracted from castor beans and is known to have an average lethal dose of 0.2 milligrams (1/5,000th of a gram), though some sources give higher figures . It is considered to be twice as deadly as cobra venom.
Toxicity and manufacture
Ricin is poisonous if inhaled, injected, or ingested, acting as a toxin by the inhibition of protein synthesis. There is no known antidote; only symptomatic and supportive treatment is available. Long term organ damage is likely in survivors. In small doses, such as the typical dose contained in a measure of castor oil, ricin causes digestive tract cramps. Ingested in larger doses, ricin causes severe diarrhea and victims can die of shock. (See abrin).
Although the castor bean plant has long been noted for its toxicity, ricin was first isolated and named in 1888 by Hermann Stillmark . Modern feed-making techniques break down the ricin in castor beans by heating at 140 degrees Celsius for 20 minutes, although some studies suggest that residual toxic effects may linger .
Ricin consists of two distinct protein chains that are linked to each other:
- Ricin A is toxic to the cell by interfering with RNA function, and thus protein synthesis
- Ricin B is important for assisting ricin A into a cell by binding with a cell surface component.
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 if and only if 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.
As few as one Castor Bean, about 0.5 grams, may be fatal in a child.
Use as a chemical/biological warfare agent
The United States investigated Ricin as for its military potential during the First World War. At that time it was being considered for use either as a toxic dust or coated bullets and shrapnel. The dust cloud concept could not be adequately developed, and researchers believed the coated bullet/shrapnel concept was unethical. 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 (LCt50 <30 mg*min/m3). 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 hospital a few days later; the pellet was discovered entirely by happenstance.
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 defined as a "schedule one" controlled substance. Despite this, more than 1 million metric tons of castor beans are processed each year, and approximately 5% of the total is rendered into a waste containing high concentrations of ricin toxin .
To put ricin used as weapon into perspective, it is worth noting that as a biological weapon or chemical weapon, ricin may be considered as not very powerful, if only in comparison with other poisons such as botulinum or anthrax. Hence, a military willing to use biological weapons and having advanced resources would rather use either of the latter than ricin. That is, though easy to produce, it is not as practical nor likely to cause as high casualities as other agents. Ricin degrades (ie, the protein changes structure and becomes less dangerous) much more readily than, for example, anthrax spores. (Jan van Aken, an expert on biological weapons explained in an interview with the German magazin Der Spiegel that he judges it rather reassuring that Al Qaeda experimented with ricin as it suggests their inability to produce botulin or anthrax.)
Pure ricin could be dispersed through the air, however it would tend to be oxidized and rendered harmless by ozone, nitrogen oxides, and other pollutants in a matter of minutes. Since it acts as an enzyme, catalyzing destruction of ribosomes, even a single oxidation is likely to render the ricin molecule harmless. Presumably it could be sealed inside some sort of dust particle that would dissolve in water, but this would be difficult.
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 toxins, but those are more difficult to obtain.
The inventors named in US Patent 3,060,165 (3 Jul 1952) "Preparation of Toxic Ricin", assigned to the U.S. Secretary of the Army, are Harry L. Craig, O.H. Alderks, Alsoph H. Corwin, Sally H. Dieke, and Charlotte Karel.
The patent was removed from the USPO database at the request of the US Army (or Department of Homeland Security), but is still available online.
Ricin-related arrests in Britain in 2003
It was widely reported in the media that traces of ricin were detected by British police in a flat in Wood Green, North London after a raid on a suspected ring of terrorists on 5 January, 2003. Media reports stated that a group was suspected of intending to use the poison in an attack on the London Underground. However at the trial of Kamel Bourgass in 2005 it became apparent that within two days of the raid the leader of the Biological Weapon Identification Group at Porton Down, Martin Pearce, had concluded that ricin was not present at Wood Green  . Some acetone, 22 castor beans, and poor recipes for ricin and other poisons copied from the Internet were found. It appears that an individual conducting some amateur research on poisons was found in this raid.
A little later several arrests were made in France and a bottle of something that tested positive for ricin was found. Further analysis identified the material as ground wheat germ. The analytic confusion was caused by the similarity of many plant proteins to one of the ricin components, which suggests that higher quality (better specificity and sensitivity) analytic tests for ricin are needed.
Six more suspects were arrested in Bournemouth in England in connection with the investigation into the alleged ricin incident in London. They were not convicted of any poisons related crime.
Three more suspects were arrested in Manchester in England in connection with the investigation of the alleged ricin found in London, following a raid carried out pursuant to an investigation into immigration issues. A Special Branch policeman, Stephen Oake , was fatally stabbed during the arrests, and three other officers were also injured, one seriously.
On January 20, 2003 Finsbury Park mosque was raided by police, apparently as part of the investigation into the alleged discovery of ricin in Wood Green. A number of men who were apparently living at the mosque were arrested.
In April 2005 31-year-old Kamel Bourgass was jailed for 17 years after being convicted of conspiracy to commit a public nuisance "by the use of poisons and explosives to cause disruption, fear or injury". He was also jailed for life following a conviction for murdering a Special Branch officer, DC Stephen Oake, who went to arrest him.
Ricin in Washington, D.C.
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.
Ricin in popular culture
The Penn and Teller book How To Play With Your Food (ISBN 0679743111) includes a "gimmicks envelope" of small objects related to the tricks inside the book. One of these is a sticker reading "With all-natural ricin!". The book explains that ricin is a poison.
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