A maximum credible event is one that could cause a large loss of life in addition to disruption, panic, and overwhelming use of civilian health care resources. This possibility brings about an attempt to evaluate and discuss substances that could be used as agents of biological warfare or as weapons of mass destruction (WMD).
An agent considered capable of causing a maximum credible event is highly lethal, inexpensively and easily produced in large quantities, stable in aerosol form, and can be dispersed. The ideal agent is also communicable from person to person and has no treatment or vaccine.
Ricin is a potent toxin that could be used as an agent of biological warfare or as a WMD. Derived from the beans of the castor plant (Ricinus communis), Ricin is native to Africa and common in warm climates worldwide. More than 1 million tons of castor beans are processed every year worldwide. It is easily and inexpensively produced, is highly toxic, and is stable in aerosolized form. Ricin has no treatment or vaccine, but it is not communicable from person to person.
Although a large amount of ricin would be necessary to produce many casualties, it would be highly effective within a closed environment. Ricin can be disseminated as an aerosol, by injection, or as a food and water contaminant. Its use as a food and water contaminant is a major concern. If ricin were used in that fashion, resultant deaths could overwhelm local health care resources.
Even use without casualties can be disruptive. Three US Senate office buildings closed on February 3, 2004, after ricin was found in the mailroom that serves Senate Majority Leader Bill Frist’s office. No injuries were reported.
On February 4, 2004, as part of the ongoing investigation as to the source of this most recent ricin attack, the Secret Service acknowledged that ricin had also been found at a White House mail-processing center in early November 2003.
A vial containing ricin was also found at a post office in Greenville, South Carolina, in October 2003. The envelope, addressed to the US Department of Transportation, was labeled “caution RICIN POISON.” The letter, protesting a proposed federal limit on the number of truckers’ hours behind the wheel to go into effect in January 2004, was signed “Fallen Angel.”
Officials suspect that the attacks in October 2003 and November 2003 are related because both letters were signed “Fallen Angel” and contained ricin of poor quality. The FBI is currently investigating whether these two earlier attacks are at all related to the ricin found in the Senate mailroom.
From 1991-1997, 3 cases involving ricin were reported in the United States.
In Minnesota, 4 members of the Patriots Council, an extremist group that held antigovernment and antitax ideals and advocated the overthrow of the US government, were arrested in 1991 for plotting to kill a US marshal with ricin. The ricin was produced in a home laboratory. They planned to mix the ricin with the solvent dimethyl sulfoxide (DMSO) and then smear it on the door handles of the marshal's vehicle. The plan was discovered, and the men were convicted.
In 1995, a man entered Canada from Alaska on his way to North Carolina. Canadian custom officials stopped the man and found him in possession of several guns, $98,000, and a container of white powder, which was identified as ricin.
In 1997, a man shot his stepson in the face. Investigators discovered a makeshift laboratory in his basement and found agents such as ricin and nicotine sulfate.
The use of ricin is not limited to the United States.
In December 2002, 6 terrorist suspects were arrested in Manchester, England. Their apartment was serving as a "ricin laboratory." Among them was a 27-year-old chemist who was producing the toxin.
On January 5, 2003, British police raided 2 residences around London and found traces of ricin, which led to an investigation of a possible Chechen separatist plan to attack the Russian embassy with the toxin. Several arrests were made.