What is Ricin?

Ricin, one of the deadliest naturally occurring poisons, is a toxin derived from castor plant beans. Castor beans are grown worldwide and are used to produce medicinal castor oil. The mash left behind after the oil is extracted contains five to seven per cent ricin.

The chemical, which is many times more deadly than cyanide, is considered a likely bio-warfare agent and is on the Centre for Disease Control and Prevention's "B" list of agents -- considered a moderate threat.

HOW IS IT PRODUCED?

Although the castor bean mash is normally rendered harmless by immersion in boiling water after crushing, it is relatively simple to extract the ricin via processes known to any graduate of chemistry.

HOW CAN IT BE USED?

A very small dose can be lethal.

The most potent method is direct injection. Ricin could also be used to poison food or drink or be inhaled in aerosol form. Less than a milligram would kill a 70 kg man. It is broken down quickly in the body and is almost impossible to trace.

WHAT ARE SYMPTOMS OF RICIN POISONING?

Injected, inhaled or ingested ricin causes flu-like symptoms. If ingested, vomiting and diarrhoea would follow. Gastroenteritis, jaundice, heart failure and organ damage are other typical effects. Death usually takes from three to five days but is not inevitable.

IS THERE AN ANTIDOTE?

Researchers at the University of Texas have been working on a vaccine and reported last year that it worked on mice. Doctors are at present only able to treat symptoms.

OTHER USES?

US researchers have for many years been experimenting with ricin as a possible treatment for cancer.

PREVIOUS KNOWN INSTANCES OF POISONING?

There have been relatively few known cases of human exposure. The most famous case was the assassination of Bulgarian dissident Georgi Markov in London in 1978. Markov was injected in the leg with ricin by a man with a poison-tipped umbrella. He died four days later. The case involved the Bulgarian secret service and the KGB.

WHO IS PRODUCING RICIN?

Iraq is suspected of working on ricin at a number of its research laboratories and is known to have produced it for military use.

In 2001, the Times newspaper reported it had found documents in an al Qaeda safe house in Kabul which proved the group was experimenting with ricin.

A ricin bomb was developed by Britain during World War 2.

- REUTERS