Toxicity of Ricin

Ricin is a potent protein toxin derived from the beans of the castor plant (Ricinus communis). Castor beans are found in many parts of the world, and the toxin can be produced simply. Ricin's significance as a potential terrorist weapon relates in part to its wide availability and ease of extraction. Ricin comprises a number of polypeptide chains that act to assist cellular uptake of the ricin molecule, cause membrane damage, and once in the cell, inhibit protein synthesis. The toxic dose in animals is low, although there is little toxicity data in humans. Most probable exposure in humans would be from inhalation of aerosols or mists containing ricin, or by ingestion. There is one established case of assassination by injection. Signs and symptoms of toxicity in humans would probably include weakness, fever, cough and pulmonary edema occuring within 18–24 hours of inhalation exposure, followed by severe respiratory distress and death from hypoxemia in 36–72 hours.