Ricin comes from the seeds of the caster bean plant, Ricinus communis. The plant is found everywhere around the world and the toxin is easily produced and the production is relatively inexpensive, therefore Ricin is potentially available worldwide. Annually one million tons of caster beans are processed to produce Caster Oil. The waste from this process is approximately 5% ricin. Ricin can be produced in a liquid or crystalline form. Ricin is also thought to be the toxin used to assassinate the Bulgarian exile Georgi Markov in London 1978. It was said that a man wielding a modified umbrella, which implanted a ricin-containing pellet into his body, attacked Georgi Markov.
Ricin is a rather stable and highly toxic through several routes of exposure, which includes through the respiratory route. Once in the system ricin attacks cells. It acts by inhibiting protein synthesis. In order to understand this, the structure needs to be known. Ricin is made of two hemagglutinins and two toxins. The toxins are made up of two polypeptide chains, chain A and chain B. Chain A is a ribosome-inactivating enzyme and chain B is the galactose /N-acetylgalactosamine-binding lectin. These chains are bonded together by a disulphide bond. Chain B binds to the surface receptors of the cell and the toxic-receptor complex is absorbed by the cell. Chain A will inhibit protein synthesis due to its endonuclease activity. The exact cause of the poison is determined by the route of exposure, e.g. inhalation would be expected to cause acute lung injury.
Once in the system ricin can cause the following symptoms in about 4 – 8 hours:
1. Abdominal pain.
3. Diarrhoea which is sometimes bloody.
4. Fever has also been reported.
5. Very high white blood cell-count. In the case of Georgi Markov it was 33,000 white blood cells per mm. The normal is between 5,000 and 10,000 white blood cells per mm.
6. If inhaled it also causes weakness and cough. Following initial symptoms it causes respiratory distress and then death.
With the case of Georgi Markov the pellet was no bigger than 1.5 mm. It was estimated that the pellet contained no more than 500mg. It is also mentioned that 1 g is enough to kill 36,000 people. From chewing the beans themselves it would probable take between 2 and 8 well chewed beans. The minimal lethal dose is around 1µg / kg body weight, that means 1/15th of a milligram could kill a 150 lb. person.