What is Ricin? Poison Sent to Barack Obama and Roger Wicker

A letter addressed to President Obama tested positive for ricin, which is a highly toxic poison. Officials say the same sender was also responsible for a ricin-laced letter sent to Senator Roger Wicker (R-Miss.).

Neither Obama nor Wicker actually received the letters, of course. Since the anthrax deaths in October 2001, all mail to Capitol Hill and the White House is received at an off-site location and tested.

Ricin, a highly toxic substance derived from Castor beans, is less dangerous than anthrax but still lethal. It can kill a person in 36 hours, and there's no antidote or even a test to know if someone’s been exposed. Breaking Bad fans will remember ricin as the poison Walt packages in cigarettes when he needs someone to die in the least conspicuous way possible.

According to Senator Claire McCaskill, (DMo.), the suspect in question often writes to lawmakers, and though the sender has been identified, a name is yet to be released. The Wicker letter was postmarked in Memphis, Tennessee, and had no return address.

After preliminary field tests, an accredited laboratory has taken over and will confirm or deny the presence of ricin in Obama's letter within the next 48 hours. Initial testing can be unreliable, according to a homeland security official, and false alarms occur annually.

Touching ricin will cause a rash but likely won't kill you. But if inhaled, ingested or injected, just 500 micrograms of ricin can be lethal. That's less than a poppy seed, volume-wise. When a molecule of ricin enters a cell it prevents protein production, and the cell dies. Nausea is the first symptom. If a sufficient amount of ricin is ingested, the person may experience vomiting and diarrhea, possibly mixed with blood. Blood may also be found in the urine. Seizures are a possibility.

Within a few days liver failure occurs, followed by the spleen and kidneys. Finally death arrives, at this point mercifully, with the collapse of the circulatory system. If injected, the muscles and lymph nodes around the needle die immediately.

This is not ricin's first appearance as a method for political assassination. In 2004 the poison was found in a letter in the mail room of former Majority Leader Bill Frist's (R-Tenn.) office. No one was contaminated.

Ricin's most famous appearance on the world stage occurred in 1978 when Bulgarian dissident and journalist for the BBC Georgi Markov was crossing the Waterloo Bridge in London and felt a sharp pain in his leg. He turned in time to see a man with an umbrella hop into a cab. The umbrella, which was supplied by the KGB, fired a minuscule pellet filled with ricin into Markov's calf, leaving only a painful pimple.

Though there have been no exposures reported yet in this most recent ricin-related incident, the story is still developing. NBC reports that the FBI did not find a connection between the letters and the attack on the Boston Marathon.