Claim: Ricin is poisonous.

Ricin -LRB- -LSB- ˈraɪsɪn -RSB- -RRB- is a highly toxic , naturally occurring lectin -LRB- a carbohydrate-binding protein -RRB- produced in the seeds of the castor oil plant , Ricinus communis . A dose of purified ricin powder the size of a few grains of table salt can kill an adult human . The median lethal dose -LRB- LD50 -RRB- of ricin is around 22 micrograms per kilogram of body weight if the exposure is from injection or inhalation -LRB- 1.78 milligram for an average adult -RRB- . Oral exposure to ricin is far less toxic as some of the poison is inactivated in the stomach . An estimated lethal oral dose in humans is approximately 1 milligram per kilogram .