Ricin is hard to turn into a terrorist weapon that can kill large numbers of people, experts say. But the lethal poison, easy to produce from a common plant, became a weapon of mass disruption when it shut down all three Senate office buildings in Washington yesterday.
"It's great for headlines, but it's not much of a weapon," said George Bean, a cell biologist at the University of Maryland, College Park.
Jonathan B. Tucker, a senior researcher at the Monterey Institute of International Studies, called ricin "really only an assassination weapon, not a mass casualty weapon. A number of countries, including Iraq, explored using ricin as a battlefield weapon and abandoned it."
Unlike fine anthrax powder, which can float through a building and infect those who breathe it in, ricin appears to be hard to turn into an inhalable powder. Since no ricin was found on air filters in the Senate mailroom where the poisonous powder was discovered, the particles apparently were too large to become airborne, Tucker said.
In light of that, closing the Senate office buildings may have been unnecessary, Tucker said.
"I think the reaction is somewhat exaggerated," he said. "Whether we should respond with this level of alarm when no one has even become sick is a real question."
Elin A. Gursky of the ANSER Institute for Homeland Security in Arlington, Va., disagreed, saying the closure was probably justified, given the government's experience with the anthrax attacks that killed five people in 2001.
"We're still very much operating out of an abundance of caution," said Gursky, who has studied the anthrax response. "Though it disrupts our lives, it gives us a chance to test our systems."
Ricin (pronounced RICE-in) is a natural toxin produced by the castor bean plant, ricinus communis, whose round, half-inch seeds are pressed to pro- duce castor oil. Once a common laxative, the oil is mostly used today as an industrial lubricant.
The poison is found in the solid part of the castor bean, which can be dissolved in a solution, dried in crystalline form and ground into powder.
When swallowed, injected or inhaled, ricin mounts a devastating attack on the body by interfering with cells' ability to synthesize proteins, said Bean. "This is one of the most toxic substances that exists," he said.
Symptoms such as vomiting and diarrhea and difficulty breathing begin within hours, and death from multiple organ failure follows within two or three days, according to medical reference books. There is no effective antidote or therapy.
That's the bad news. But using ricin to poison a large number of people would be difficult, experts say.
Because it has a bitter taste and produces a burning sensation in the mouth, potential victims would be unlikely to consume much poisoned food, Bean said. Poisoning a water supply would require a huge amount of ricin, and routine water treatment weakens or destroys the poison.
In theory, an aerosol of fine ricin powder could poison a crowd, and animal tests have proved that fatal inhalation of ricin is possible.
But no human case is known, and producing an effective ricin aerosol for military use was so difficult that the attempt was abandoned by the United States in the 1950s and by Iraq in the 1980s.
For assassination, on the other hand, ricin has made a name for itself. Georgi Markov, a Bulgarian dissident writer, was injected with a ricin pellet when a Bulgarian agent jabbed his thigh with a poison-tipped umbrella as he approached a London bus stop in 1978. He grew severely ill the next day and died four days later.
Authorities discovered the cause of Markov's death only after connecting it to a similar attack survived by another Bulgarian dissident in Paris 10 days earlier. In a memoir years later, former Soviet KGB Gen. Oleg D. Kalugin acknowledged that he had been ordered to provide the assassination tools to the Bulgarian secret police.
Americans have been charged a half-dozen times over the past decade with plotting to use ricin to kill or threaten others in domestic disputes. In 1995, a right-wing extremist group in Minnesota called the Patriots Council was accused of producing ricin to use against Internal Revenue Service agents and other law enforcement officers.
No deaths resulted from the alleged plots, which sometimes relied on ricin recipes found on the Internet.
"The technology threshold for this material is so low that someone could make it in their basement," Tucker said.
Operatives of the al-Qaida terrorist network have also shown interest in ricin. The discovery of ricin traces in a London apartment a year ago resulted in the arrest of six men of North African origin and set off a wave of fear in England.