Dr. Salim Surani explained where ricin comes from, why it is beneficial if properly administrated and deadly at the same time. The CDC labels ricin as a poison found naturally in castor beans. If castor beans are chewed and swallowed, the released ricin can cause injury. Ricin can be made from the waste material left over from processing castor beans. It can be in the form of a powder, a mist, or a pellet, or it can be dissolved in water or weak acid.