The Five Most Deadly Chemical Weapons of War

"Chemical weapons require a relatively low investment, can cause severe psychological and physical effects and are agents of disruption."

The three year crisis in Syria has led to a resurgence of interest in chemical weapons. Often referred to as the “poor man’s bomb,” chemical weapons require a relatively low investment, can cause severe psychological and physical effects and are agents of disruption.

Modern chemical weapons were introduced during World War I in an effort to reduce the deadlock of trench warfare. But they are subject to topography and weather patterns. As munitions have become more precise, their tactical advantage is being eroded. Today, they horrify more than they contribute to victories on the ground. Their indiscriminate nature and unpredictability, coupled with the sometimes-gruesome effects they have make them effective weapons of fear.

Below are five of the worst chemical weapons:

Most toxic: VX

VX belongs to organophosphorus compounds and is classified as a nerve agent because it affects the transmission of nerve impulses in the nervous system. It is odorless and tasteless in its pure form, and appears as a brownish oily liquid.

Developed in the UK in the early 1950s, VX is particularly potent because it’s a persistent agent: Once it’s released into the atmosphere it’s slow to evaporate. Under regular weather conditions, VX can persist for days on surfaces, while it can last for months in very cold conditions. “VX vapor is heavier than air,” which means that when released, “it will sink to low-lying areas and create a greater exposure hazard there.” Such characteristics make VX potentially useful as an area-denial weapon.

VX is also a fast-acting agent. Symptoms can appear only seconds after exposure. They include salivation, constriction of the pupils and tightness in the chest. As with other nerve agents, VX works by affecting the enzyme (acetylcholinesterase) that acts as the body’s ‘off switch’ for glands and muscles. With the enzyme blocked, molecules constantly stimulate the muscles. As the muscles spasm, they tire. Death is caused by asphyxiation or heart failure. While it is possible to recover from exposure, tiny amounts of the agent can be lethal.

Most recently used: Sarin

In September 2013, the UN confirmed that a chemical weapons attack involving specially designed rockets that spread sarin over rebel-held suburbs of the Syrian capital took place the month before. UN Secretary General, Ban Ki-Moon stated that this was the “most significant confirmed use of chemical weapons against civilians since Saddam Hussein used them in Halabja in 1988.”

Sarin (also known as GB) is a volatile but toxic nerve agent. A single drop the size of the head of a pin is enough to kill an adult human rapidly. It is a colorless and odorless liquid at room temperature, but evaporates rapidly when heated. After release, sarin will spread into the environment rapidly and present an immediate but short-lived threat. Similar to VX, “symptoms include headaches, salivation and secretion of tears, followed by gradual paralysis of the muscles” and possible death.

Sarin was developed in 1938 in Germany when scientists were researching pesticides. The Aum Shinrikyo cult used it in a 1995 attack on the Tokyo subway. While the attack caused mass panic, it only killed 13 because the agent was dispersed in liquid form. In order to maximize casualties, not only must the sarin be a gas, but the particles need to be small enough so they are easily absorbed through the lining of the lungs, yet heavy enough that they are not breathed back out. Sarin is not easy to weaponize.

The quality of the agent also matters. Sarin (and VX) is susceptible to degradation, especially if it isn’t pure. Iraq’s sarin for example, had a shelf life of about one to two years. While the degraded products are still toxic, they can’t be used as weapons. Although Syria’s CW stockpile was growing old and the agents were likely to have deteriorated significantly, the sarin used in the attack on the Ghouta suburbs on August 21, 2013 was higher quality than that used in the 1995 Tokyo attack or in Halabja. But it was still a far cry from the sarin produced by the United States and the Soviet Union.

Most popular: Mustard Gas

Also known as sulphur mustard, this agent gets its name from its trademark rotten mustard or garlic and onion odor. It belongs to the group of blister agents (or vesicants) that work by targeting the eyes, respiratory tract and skin, first as an irritant and then as poison for the body’s cells. It’s particularly grisly and slow acting. When skin is exposed to it, it reddens and burns for a few hours before large blisters appear and cause severe scarring and pain. Eyes will swell, tear and possibly go blind a few hours after exposure, and when inhaled or ingested, victims will experience sneezing, hoarseness, coughing up blood, abdominal pain and vomiting.

But exposure to mustard gas is not always fatal. When it was first used in WW1, it killed only 5 percent of those exposed. It became a popular chemical weapon—used in both world wars, during the civil war in Yemen and the Iran-Iraq war—because of its properties.