The Castor Bean

The ca­stor bean plant, or Ricinus communis­, is widely cultivated for its castor oil and is also used as an ornamental plant. Neither of these uses would clue you into the fact that this plant has deadly contents: ricin.

Castor oil is a mild-tasting vegetable oil that is used in many food additives, flavorings and in candy production. It's also available to the consumer as a laxative and to induce labor (though no scientific evidence shows it's successful in inducing labor). Castor oil comes from the plant's seeds, which are 40 to 60 percent oil.

­The castor bean plant probably originated in Africa, but is now found throughout the world. This large, shrubby plant is popularly used in gardens because of its hardy nature. It grows well in barren areas and doesn't require special care. It's fast-growing and can reach 36 feet (11 meters) in a season. The flowers of the plant are yellowish green, and the centers of the flowers are red. The leaves are large with toothed edges.

Ricin is present in low levels throughout the plant, but it is largely concentrated in the seed coating. Seed poisonings are rare and usually involve children and pets, but they can be deadly. As few as three seeds, which are green with brown markings, could kill a child who swallows them.

Symptoms of castor bean poisoning include nausea, abdominal cramps, vomiting, internal bleeding, and kidney and circulation failure. Many people suffer from an allergic reaction to the dust from the seeds and may experience coughing, muscle aches and difficulty breathing. Exposure to the dust is most common in areas where the beans are processed for commercial use. In ancient times, the castor bean was used in ointments, and allegedly, Cleopatra applied the oil to the whites of her eyes to brighten them.

All-natural Murder
Well-known Bulgarian writer Georgi Markov defected from Bulgaria in 1969, when Bulgaria was still a Communist state. Once he settled in England, he took a job as a journalist and broadcaster for BBC World Service and Radio Free Europe. Bulgarian government officials were not pleased when Markov developed a broadcast titled "In Absentia -- Reports" about life in Communist Bulgaria. So they made arrangements to silence him for good.

­As Markov stood at the bus stop one day, he felt a sharp jab in the back of his leg. When he turned, a man apologized for poking him with his umbrella. Three days later, Markov was dead. During an autopsy, physicians removed a metal pellet the size of a pin head from Markov's calf. The pellet was hollow in the center and contained traces of ricin [source: Center for Disease Control].