Castor Oil Residue Is Among Deadliest Poisons

January 8, 2003
By Mark Henderson, Science Correspondent

RICIN is one of the deadliest naturally occurring poisons known to man. It is also among the most readily available to terrorists.

The toxin, which can kill in tiny concentrations, comes from the seeds of the castor bean plant, Ricinus communis, which is grown legitimately all over the world to make castor oil — an industrial lubricant, a leather curing agent and a laxative.

About a million tonnes of castor oil are produced every year, and the mash left behind as waste can contain as much as 5 per cent ricin by weight. Although the toxic waste is normally rendered harmless by immersion in boiling water, the poison can be extracted with a relatively simple chemical process. Anyone with a biochemistry degree could master it, according to scientists.

As well as being easy to make in large amounts, it is highly stable, which makes storage and transport straightforward. While ricin has traditionally been used as a weapon of assassination rather than one of mass destruction, these qualities have made it highly attractive to modern terrorists.

Ricin is four times more toxic than cobra venom and, when injected, can kill with a dose as small as one microgram per kilogram of bodyweight. This means that as little as 70 micrograms — about the weight of a grain of salt — can be enough to kill an average-sized adult. It can also be deadly when eaten or inhaled, although at higher doses: 3 micrograms per kilogram for inhaled ricin; and 30 micrograms per kilogram for ingested toxin.

It works as a cytotoxin, or cell poison, with a single molecule capable of killing a cell by shutting down its life-support functions. Within three hours of poisoning, the victim will experience abdominal pain, vomiting and diarrhoea, often with blood in the stools, and this will be followed by severe dehydration, reduced blood pressure and collapse of the liver, kidneys and lungs. Death usually occurs within three to five days. Although there is no antidote, doctors can reduce the death-rate by managing the symptoms, in particular making sure the patient is properly hydrated.

Dr Thomas Stuttaford, the Times doctor, said: “It is in a completely different category from other, more common forms of poison, such as arsenic and prussic acid. I would say that it is one of the most lethal poisons available. Only a tiny drop is needed to kill someone.” Eight castor oil seeds contain enough ricin to kill an adult; one to three beans could kill a child.

Bioterrorism experts believe that the toxin is most likely to be used by poisoning food or water supplies. “The primary aim of these people is to cause panic and fear, and the simplest way of doing this would be to put it in food, to infect something on the supermarket shelves,” John Eldridge, editor of Jane’s Nuclear, Biological and Chemical Defence, said.

“It would be not unlike the cases where people have injected rat poison into Mars bars or mercury in oranges, but the reaction of society would be out of all proportion to the risk.”

An alternative would be to make the poison as an aerosol and release it. This, however, would be much harder to achieve as the quantities required would be much greater. The amount of ricin spray needed to kill half the population of a 60 square mile area is four tonnes.

Another possibility would be for terrorists to use it to spread fear with a campaign of political assassinations. Dr Stuttaford said: “I don’t think it would be that effective as a weapon to be used to wage mass terror. It does not have that capability. It could, however, be used to create alarm and despondency among the ruling classes as prominent people died inexplicably. All they would feel is a light pinprick and soon they would be dead. Everyone would be asking: ‘Who’s next?’ It would create panic of a different order from, say, anthrax or smallpox.”

Mr Eldridge said that simple agents such as ricin could present a greater risk than the nerve gases and diseases more often associated with biological or chemical terrorism. “I think there is a danger that society is looking so hard down the rabbit hole of anthrax and other complicated agents that we’re missing what these coves are really doing: looking for the simplest ways of causing maximum disruption.”

Several Middle Eastern countries, including Iraq, are known to have produced ricin as part of biological weapons programmes. A ricin bomb was also developed by Britain during the Second World War, when it was codenamed Compound W by the Porton Down biological weapons establishment in Wiltshire.
http://www.timesonline.co.uk/article/0,,2-536105,00.html