Fast Facts: Sarin

What Is It?

Sarin (search) is a colorless and odorless gas and is lethal in doses as small as .5 milligrams. Experts say sarin is more than 500 times as toxic as cyanide. It's current use is predominantly as a military chemical nerve agent. Sarin emits very toxic fumes of fluoride and phosphorus oxides when heated to decomposition or reacted with steam. At room temperature, sarin takes a liquid form, but it evaporates quickly into a gas. Sarin acts and dissipates more quickly than other nerve agents.

This chemical weapon is most known for the March 1995 terrorist attack by the Aum Shinrikyo (search) religious cult, when members released the gas at several points in the Tokyo subway system, killing 11 and injuring more than 5,500. The perpetrators left punctured packages of liquid sarin in subway cars and stations, which gave officials time to seal off the affected areas. The more serious cases involved cardiopulmonary or respiratory arrest with marked miosis (pinpoint eye pupils). Major signs and symptoms in victims were miosis, headache, dyspnea, nausea, ocular pain, blurred vision, vomiting, coughing, muscle weakness and agitation. Although these physical signs and symptoms disappeared within a few weeks, psychological problems associated with posttraumatic stress disorder persisted longer.

This was the second civilian sarin gas incident caused by that cult in less than one year. In the first incident, Aum Shinrikyo killed seven and injured more than 200 people when they released sarin in the central Japanese city of Matsumoto.

What Are the Symptoms of Exposure?

Death may occur within one to 10 minutes of inhalation exposure to even a small amount of sarin.

The first indication of exposure to sarin may be at the point of contact and can include sweating, muscular twitching and miosis. Runny nose, tightness of the chest, shortness of breath and dimness of vision may also be experienced. In more severe cases, a victim may experience headache, cramps, nausea, vomiting, involuntary defecation and urination, twitching, jerking, staggering, convulsions, drowsiness, coma and respiratory arrest.

How Is It Treated?

Atropine is the classic antidote for nerve agents. If administered immediately, it relieves symptoms and helps keep the nervous system functioning. Another family of drugs, known as oximes, helps restore muscle control. In many countries, armed forces carry auto-injectors containing a combination of atropine and an oxime.

Immediate decontamination of the smallest drop is essential. Effects may be delayed in the case of exposure to skin, or dermal exposure.

In the case of eye exposure, eyes must be flushed with lukewarm water for at least 15 minutes. Exposed skin should be washed thoroughly with liquid bleach, then doused in water. If sarin is ingested, health care officials are encouraged to promote excretion by administering a saline cathartic or sorbitol to conscious victims.

Who Has It/Where Can It Be Found?

Only Russia and the United States have officially declared that they have stockpiles of sarin. The United States began developing sarin as part of its chemical weapons program in the 1950s; it now has more than 5,000 tons of the substance. Russia has about 11,700 tons.

Other countries may also have sarin stockpiles. India and South Korea have chemical warfare agents, but it's unknown whether they have sarin. Iraq began producing sarin in 1984 and admitted to possessing 790 tons of it in 1995. In May 2002, the Bush administration accused Syria of having a sarin stockpile. Experts also suspect Egypt, Iran, Libya, and North Korea of having sarin. There are unconfirmed reports of sheltered Scud missiles with sarin or tabun nerve gas warheads deployed in caves and shelters near Damascus, Syria.

Saddam Hussein used sarin along with mustard gas on the Kurds in northern Iraq during Anfal and in 1988 in Halabja. Experts say Saddam also launched about 280 smaller-scale chemical attacks against the Kurds.

There are unconfirmed reports that Afghanistan's ousted Taliban rulers and Al Qaeda tried to make chemical weapons, including sarin and VX. U.S. officials say they're aware of Al Qaeda's interest in possessing such weapons but haven't accused the group of actually having them.