What is ricin?

Ricin is a poison that can be made from the waste left over from processing castor beans, above. It can be in the form of a powder, a mist or a pellet, or it can be dissolved in water or weak acid.

It would take a deliberate act to make ricin and use it to poison people. Accidental exposure to ricin is highly unlikely.

Depending on the type of exposure, as little as 500 micrograms -- about the size of the head of a pin -- could be enough to kill an adult. Per gram, it's 6,000 times more deadly than cyanide.

There is no vaccine available.