Ricin consists of two parts: Ricin A, common to many foods and toxic within the cell by stopping RNA, and thus protein synthesis; and Ricin B, unique to ricin and required for bringing Ricin A into a cell by meshing with a cell surface component. Inducing Ricin B antibodies in humans may have been done.
Although the castor bean plant has long been noted for its toxicity, ricin was first isolated and named in 1888 by H. 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 is easily purified from castor-oil manufacturing waste. The seed-pulp left over from pressing for oil is on average 5% by weight ricin. Since 200mcg constitute a fatal dose, this is a considerable amount of ricin.
Use as a chemical/biological warfare agent
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 shot him with a modified umbrella using compressed gas to fire a pellet containing ricin.
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 100 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 .
Ricin-related arrests in Britain in 2003
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 in January 2003. The group is suspected of intending to use the poison in an attack on the London subways.
Six more suspects have been arrested in Bournemouth in England in connection with the investigation into ricin found in London.
Three more suspects have been arrested in Manchester in England in connection with the investigation into ricin found in London, although it now appears as though the raid was initially 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 discovery of ricin in Wood Green. A number of men who were apparently living at the mosque were arrested.