Ricin — a toxin extracted from castor beans – is not, as being reported, a biological weapon. It is a very potent chemical weapon. A dose as small as one milligram can kill an adult. Biological weapons cause disease. Chemical weapons — such as ricin or the nerve gas VX — poison. Exposure to ricin is not infectious. All chemical weapons require ingestion into the body, by breathing, absorption through the skin, or other intake. Ricin poisoning, unlike many biological weapons such as anthrax, and some other chemical weapons, is not treatable.