U.S. Capitol policemen dressed in biochemical hazard gear check their gas masks as they make their way into an elevator at the Dirksen Senate Building in Washington, Feb. 2, 2004.
Ricin is a poison easily made from the castor oil plant.
Senate Majority Leader Bill Frist says tests so far identify a white powder found in his office Monday as the deadly poison ricin, and a criminal investigation is under way. All Senate office buildings have been shut down and committee hearings cancelled.
Officials say air-sampling studies show the substance has not been detected outside of Frist's office, and there are no reported illnesses.
Capitol police are advising lawmakers not to open any mail. Letters and packages to congressional offices have been irradiated since the 2001 anthrax attack, but radiation would not have an effect on ricin. NPR's Allison Aubrey reports.
Facts on ricin's potential as a bioterrorist weapon, excerpted from the Centers for Disease Control and Prevention:
What Ricin Is
Ricin is a poison that can be made from the waste 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.
How Ricin Is Used
Castor beans are processed throughout the world to make castor oil. Ricin is part of the waste "mash" produced when castor oil is made.
Ricin has some potential medical uses, such as bone marrow transplants and cancer treatment (to kill cancer cells).
Exposure to Ricin
It would take a deliberate act to make ricin and use it to poison people. Accidental exposure to ricin is highly unlikely.
People can breathe in ricin mist or powder and be poisoned.
Ricin can also get into water or food and then be swallowed.
Depending on the route of exposure (such as injection), as little as 500 micrograms of ricin could be enough to kill an adult. A 500-microgram dose of ricin would be about the size of the head of a pin. A much greater amount would be needed to kill people if the ricin were inhaled or swallowed.
Ricin poisoning is not contagious. It cannot be spread from person to person through casual contact.
Signs and Symptoms of Exposure
The major symptoms of ricin poisoning depend on the route of exposure and the dose received, though many organs may be affected in severe cases.
Initial symptoms of ricin poisoning by inhalation may occur within 8 hours of exposure. Initial symptoms of ricin poisoning by ingestion typically occur in less than 6 hours.
Inhalation: Within a few hours of inhaling significant amounts of ricin, the likely symptoms would be difficulty breathing, fever, cough, nausea and tightness in the chest. Heavy sweating may follow as well as fluid building up in the lungs (pulmonary edema). This would make breathing even more difficult, and the skin might turn blue. Finally, low blood pressure and respiratory failure may occur, leading to death.
Ingestion: If someone swallows a significant amount of ricin, he or she would develop vomiting and diarrhea that may become bloody. Severe dehydration may be the result, followed by low blood pressure. Other signs or symptoms may include hallucinations, seizures and blood in the urine. Within several days, the person's liver, spleen and kidneys might stop working, and the person could die.
Skin and eye exposure: Ricin in the powder or mist form can cause redness and pain of the skin and the eyes.
Death from ricin poisoning could take place within 36 to 72 hours of exposure, depending on the route of exposure (inhalation, ingestion or injection) and the dose received. If death has not occurred in 3 to 5 days, the victim usually recovers.