Ricin

Ricin is in the news again, following the discovery of an envelope containing ricin powder in Senator Bill Frist’s mail. This highly toxic, plant-based substance is considered to be a prime candidate for use as a chem./bio terrorist weapon. Interestingly, the parents and grandparents of many baby-boomers probably routinely used a derivative of this same plant – castor oil! We’ve compiled a fact sheet about ricin and the castor bean plant from information provided by the Centers for Disease Control and Prevention.

Clinical and Emergency Preparedness Resources on Ricin

Ricin is present throughout the castor bean plant (Ricinus communis), but it's primarily concentrated within the castor bean.

Castor bean plants are common outdoor plants that are often used as an ornamental garden plant. They are large shrubs that can grow as high as 12 feet.

These plants are native to Africa and common in warm climates worldwide.

More than 1 million tons of castor beans are processed every year worldwide.

Castor beans are a commercial source of castor oil, which is extracted from the castor bean and used as an industrial lubricant, as a medical purgative, and as a laxative.

Castor oil itself contains no ricin.

During the preparation of castor oil, the ricin-containing resin portion of the plant is separated from the non-ricin-containing oil portion.

Ricin can be prepared in three different forms: liquid, crystalline, or dry powder. Ricin is water soluble, odorless, tasteless, and stable under ambient conditions.

Ricin is one of the most toxic biological agents known -- a Category B bioterrorism agent and a Schedule 1 chemical warfare agent.

Because the ricin protein is large, it is probably not well absorbed orally or through the skin.

Although ricin is less toxic by the oral route compared with inhalation and injection, there are hundreds of reported cases of toxicity, and several fatalities, from castor bean [chewing] and ingestion.

At this time there is very limited knowledge about the human effects of ricin poisoning.

Most cases of non-terrorism ricin poisoning involve [chewing] and ingestion of castor beans.

Occasionally, workers in or around castor oil processing plants experience respiratory or dermal symptoms from exposure to castor bean dust, presumably related to an allergic syndrome.

Because ricin has been shown to inhibit tumor growth, clinical trials investigating intravenous low-dose ricin as a potential chemotherapeutic agent have been performed.

The chemical and physical properties of ricin make it a potential agent for use as a terrorist weapon. Ricin would need to be dispersed in particles smaller than 5 microns to be used as an effective terrorist or military weapon by the inhalational route. It is very difficult to prepare particles of this size. Ricin could also be used as a terrorist weapon through the contamination of food, beverages, or potentially some consumer products.

Exposure to ricin may occur through:

• Inhalation, [skin], or [eye] contact: as an aerosol, powder, or dust
• Ingestion: through contamination of food, water, or consumer products
• Parenteral: directly injected into a target

Systemic toxicity has been described in humans only following ingestion or injection of ricin into the body. Based on limited animal studies, ricin is expected to be a much more potent toxin when inhaled or injected, compared with the other routes of exposure.

There are no reports of people who have ingested purified ricin toxin.

Ingestion and [chewing] of 3 - 6 beans is the estimated fatal dose in adults. The fatal dose in children is not known but is most likely even less.

Symptoms of mild toxicity including nausea, vomiting, diarrhea, and/or abdominal cramping are invariably present in people who chew and ingest a significant amount of castor beans. …symptoms typically resolve within 24 hours.

Moderate to severe toxicity may include: gastrointestinal symptoms - that is, persistent vomiting and voluminous bloody or nonbloody diarrhea, which typically leads to significant fluid losses.

In severe poisoning, hepatic (liver) and renal failure and death are possible within 36 - 72 hours of exposure.

Unintentional sublethal aerosol exposures to ricin which occurred in humans in the 1940s were characterized by onset of the following symptoms within 4 - 8 hours: fever, chest tightness, cough, dyspnea (difficulty breathing), nausea, and arthralgias (joint pain) followed by diaphoresis (sweating).

The current body of knowledge, based on limited human and animal data, suggests that significant poisoning through inhalation, ingestion and parenteral exposure would consist of a relatively rapid progressive worsening of symptoms over approximately 4 to 36 hours from exposure.

Source: CDC - Public Health Training Network

CDC provides a Webcast giving clinicians and public health officials the most up-to-date information available on recognition, management, and disposition of patients with ricin-associated illness; identification of epidemiologic clues possibly associated with a covert ricin release; and disposition of patients with suspected ricin-associated illness.