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BZ: Its history, symptoms, effects

Some have speculated that the Russian government used BZ gas as the incapacitating agent to end the Moscow theater siege. NBC’s Robert Windrem offers some background on its history, symptoms and effect.
/ Source: NBC News

Some have speculated that the Russian government used BZ gas as the incapacitating agent to end the Moscow theater siege. Here is some background on its history, its symptoms, effects and treatments:

BZ GAS WAS developed by the United States Army at the Edgewood Arsenal in Maryland during the 1950s as a military agent. It later was believed to have capability as a crowd control agent. There are no known detectors for its presence in either indoor or outdoor environments.

Although chemically based, its use or possession is not specifically prohibited by the Chemical Warfare Convention [CWC] unless produced in certain quantities.


BZ is a stable white crystalline powder that is only slightly soluble in water. It is described by the U.S. Army as a “central nervous system depressant.” It can “disrupt the high integrative functions of memory, problem solving, attention, and comprehension. A relatively high dose produces toxic delirium, destroying the individual’s ability to perform any military task.”

The Army’s field manuals describe the effect: “mild peripheral effects of BZ occur within 1 hour and maximal central effects occur after about 4 hours lasting 24 to 48 hours, with a peak at 8 to 10 hours,” indicating that Russian forces may have deployed the gas several hours before the attack.

First symptoms include dizziness, ataxia (a loss of motor control), vomiting, dry mouth, blurred vision, confusion, sedation leading to stupor, progressing to random unpredictable behavior with delusions and hallucination within 12 or more hours. The U.S. Army believed the most important single medical consideration is the possibility of heat stroke.

The U.S. Army ultimately abandoned its use because of its unpredictability on the battlefield.


It has been used several times over the past 40 years, most famously against theViet Cong in the Vietnam War by the United States and against Muslims in both Bosnia and Kosovo by Yugoslavian troops. Veterans groups over the years have charged that U.S. soldiers in Vietnam were exposed to it and suffered long-term neurological effects.

Iraq is also believed to have made BZ in 1989-90, but the United Nations could not verify the development “due to the absence of sufficient data from documents and other verifiable evidence.”

There is no evidence that it used it against either Iran or coalition forces but U.S. and British intelligence believed that “Iraq may have possessed large quantities of a chemical warfare agent known as Agent 15,” a group of chemicals that includes BZ, according to the Defense Department.


As early as 1986, the United States was aware of an Iraqi research program into BZ and another psychochemical, EA3443, at its main chemical and biological weapon R&D facility at Muthanna near Samarra.

BZ intake can be treated with a chemical called physostigmine, a compound that enhances levels of a substance (acetylcholine) between neurons in the brain. The drug has a history of successful treatment on patients suffering from carbon monoxide intoxication. Also called eserine, physostigmine has also been used to enhance memory in patients with Alzheimer’s disease.

Robert Windrem is an investigative producer at NBC News.