What is ricin?

WASHINGTON - Ricin, thought to have been detected in a United States Senate mail room this week, is one of the deadliest poisons known, easy to make and easy to conceal.

Made from the same castor bean used to make castor oil, ricin is considered a likely biowarfare or bioterrorist agent and is on the Centers for Disease Control and Prevention's "B" list of agents -- considered a moderate threat.

It is perhaps best known as the poison used to assassinate Bulgarian exile Georgi Markov in London in 1978. Markov was injected in the leg with a ricin pellet by an agent with a specially designed umbrella. He died four days later. The case involved the Bulgarian secret service and the KGB.

Ricin was also discovered in apartments in London in January 2003 that had been occupied by Islamic extremists.

Some reports have indicated ricin may have been used in the Iran-Iraq war during the 1980s and ricin was found in Al Qaeda caves in Afghanistan.

Because castor beans are processed throughout the world to make castor oil, ricin could be available to many different groups. But experts say it is not a likely weapon of mass destruction and more likely to be used on a small or even an individual scale.

The toxin can be put into food, water or even made into an aerosol and sprayed. It is broken down quickly in the body and is almost impossible to trace.

A very small dose is lethal to humans and the symptoms are frighteningly misleading. Victims feel like they have the flu for a few days and then die suddenly.

The CDC says that if injected, as little as 500 micrograms of ricin -- which would fit on the head of a pin -- could kill an adult. Much more would be needed to kill if the ricin were inhaled or swallowed.

Ricin can be delivered in the form of a powder, a mist, or a pellet, or it can be dissolved in water or weak acid. Water supplies or food can also be contaminated with ricin.

The toxin cannot be spread from person to person.

Symptoms of ricin poisoning begin within eight hours of exposure and vary depending on whether it was injected, breathed in or eaten, according to the CDC.

When inhaled symptoms include difficulty breathing, fever, cough, nausea, sweating and tightness in the chest. Death occurs after blood pressure plummets and breathing stops.

When swallowed, ricin caused vomiting, diarrhea, dehydration, low blood pressure and perhaps hallucinations, seizures and blood in the urine.

"Within several days, the person's liver, spleen, and kidneys might stop working and the person could die," the CDC says.

Ricin in the powder or mist form can irritate the skin and eyes. In all cases, death can follow within 72 hours.

"If death has not occurred in 3 to 5 days, the victim usually recovers," the CDC advises. There is no antidote although several groups are working on one.

Ricin poisoning is treated with measures including respirators if needed, fluids, flushing the stomach and treating low blood pressure.

If you suspect you are exposed to ricin, the CDC advises getting into fresh air as soon as possible.

- REUTERS