What is ricin?

What is this poison that is causing alarm in Washington?

Ricin is a potentially deadly poison found in castor beans, a by-product when castor oil is made.

According to the U.S. Centers for Disease Control and Prevention, when ricin is inhaled, it can cause difficulty breathing, leading to respiratory failure. When ingested, vital organs such as the liver, spleen and kidneys may stop working and the person could die in a matter of days.

Accidental exposure to ricin is highly unlikely, since it would take a deliberate act to produce the toxic substance, according to the CDC.

That is why the presence of a biological agent such as ricin, which tested positive in letters sent to President Obama and Sen. Roger Wicker, R-Missi., is alarming.

According to a political science professor at University of Missouri who specializes in terrorism attacks, ricin is not traditionally used to cause mass destruction, as it needs to be in close contact and does not spread like sarin gas or anthrax, said Paul Wallace.