The potential for a person to encounter ricin accidentally is so rare that the almost any cases of ricin illness would be considered the result of an attack, according to the U.S. Department of Health and Human Services (HHS).
Ricin, a biological toxin created from the waste leftover from processing castor beans that stops cells from making the proteins they need to survive, can be made into a powder that can be aerosolized. Pellets of ricin or ricin dissolved in a liquid can be ingested or injected into a person’s body.
Authorities in Georgia on Tuesday arrested four members of a militia group that were planning multiple bombings and a biological attack. Over the course of several meetings that were under surveillance by the FBI, the four men -- Frederick Thomas, 73, Dan Roberts, 67, Ray H. Adams, 65, and Samuel J. Crump, 68, discussed various attacks, including the use of explosives to target federal buildings. The group was also acquiring the means to make ricin and looking for a way to disperse the toxin while driving down the highway, the Los Angeles Times reported.
Ricin is lethal in small doses, but it's not clear how effective it the milita's plan would actually be. In 1978, an amount of ricin “the size of a pin head” was used to kill a Bulgarian journalist living in exile in London, however, scientists don’t know exactly how much ricin would be needed in an aerosol release to cause mass casualties -- nor do they know how long it would survive in the environment, according to HHS.
When it comes to ricin detection, “Almost any ricin illness would be considered an attack, since accidental ricin poisoning is extremely unlikely,” according to a guide on terrorism and public health emergencies created by HHS in 2005. “Evidence of an attack would be numerous cases of illness by people who have been in the same location or attended the same event.” Unlike anthrax, which commonly infects wild animals and still exists in nature along rural cattle trails in the United States and Canada, a person isn’t going to come into contact with ricin in the environment.
“It would take a deliberate act to make ricin and use it to poison people,” according to a CDC fact sheet, although the ingestion of castor beans could cause sickness related to ricin poisoning.