How Biological and Chemical Warfare Works

Chemical and biological agents can spread through the air, water and food supplies.
Chief Warrant Officer 2 Keith A. Stevenson/U.S. Marine Corps

With spores mailed inside envelopes, the 2001 anthrax attacks marked the first bioterrorist attacks in the United States. The spores killed five people, four of whom were not the intended targets. After considering Al Qaeda, draining ponds in search of evidence, and pursuing the wrong person, the FBI traced the letters to a domestic source -- a scientist working in biodefense. He was one of the FBI's own advisors on anthrax.

Besides proving deadly, the 2001 anthrax incident caused considerable disruption. Mail was stopped in several cities, and it cost more than $1 billion to clean up the spores [source: Lipton]. And all of this was caused by just one man. The prospect of a larger attack is beyond frightening. Terrorists can hide biological weapons in pharmaceutical production lines and breweries. The biggest eyes we have for surveillance, like spy satellites, can't inspect those very well.


So where does the U.S. stand if it's attacked again? In 2005, the presidential commission on intelligence released a report saying that while the United States was building a reasonable defense of vaccines and other measures on the ground, it was rather clueless on which countries had what biological agents [source: Lipton]. In 2009, the Department of Homeland Security predicted that the United States would see another biological attack in the next five years [source: AP].

Chemical weapons have the same potential for killing thousands of people in a city attack -- and unfortunately, a long history of doing so. Thankfully, much of the world has at least pledged to disarm itself of chemical weapons. Under the Chemical Weapons Conventions, states representing 98 percent of the world's population and the same percentage of the chemical industry are supposed to be rid of chemical weapons by 2012 [source: OPCW]. But there are enough routes around the treaties. States like North Korea didn't sign them. And signatories may have undeclared weapons. Before they are actually destroyed, weapons marked for disposal could also be stolen or sold. Still, as of December 2008, more than 40 percent of the world's declared chemical stockpile, led by the stockpilers Russia and the United States, had been destroyed [sources: Cohen, Chyba].

For all of these reasons, it's good to know what threats exist. This article will explain how chemical and biological weapons really work, how they might be deployed and what the actual threats are.

Understanding Warfare

U.S. Marines with the 15th Marine Expeditionary Unit (Special Operations Capable) head back to their decontamination area after completing an enhanced nuclear, biological and chemical defense exercise at Camp Buehring, Kuwait, in Feb. 2005.
Lance Cpl. Thomas J. Grove/U.S. Marine Corps

There is an interesting paradox when it comes to war in the modern world. Anyone who has experienced war knows that it is about death and destruction on a massive scale. People die one at a time because of bullets, bayonets, hand grenades and landmines, and they die in large groups because of cannons, bombs and missiles. Buildings, factories or entire cities get destroyed.

Despite the appearance of anarchy, warfare between modern nations does have rules. These rules, like the Geneva Conventions, for example, tend to discourage the wholesale destruction of civilians, and they govern the treatment of prisoners of war. The rules are not always followed to the letter, and many times are broken completely, but they do exist.


Chemical weapons were first used in World War I, and the nations of the world quickly and uniformly decided that these weapons went too far. Apparently, killing people with flying metal and explosives was one thing, but launching a cloud of deadly chemicals or bacteria -- the effects of which could neither be predicted nor controlled -- was another. Significant treaties prohibiting biological and chemical weapons, starting as early as the 1925 Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare, have been signed by most nations of the world.

The unfortunate problem is that terrorists and rogue leaders don't pay attention to significant international treaties.

Charles Taylor, the former president of Liberia, is one such rogue leader. Among many crimes, he is on trial for violating the Geneva Conventions during the Liberian civil war. The charges include having soldiers kill peacekeepers and rape and murder civilians [source: Crane].

Signatories have also ignored the Biological Weapons Convention. The Soviet Union signed the treaty, then secretly built a massive arsenal of biological weapons [source: New York Times].

The Chemical Weapons Conventions have been disregarded as well. Although Iraq was a signatory, Saddam Hussein rained mustard gas and sarin on Kurdish civilians in Iraq, killing thousands, during the Iran-Iraq war [sources: Burns, Chivers].

And states that don't sign the treaties, like North Korea, posses whatever they like. North Korea has sarin and anthrax weapons and is suspected of being armed with smallpox [source: Kristof].

That is where the threat of chemical and biological weapons used in random attacks on innocent civilian populations comes from.

The Basics of Chemical and Biological Weapons

Like a nuclear bomb, a chemical or biological weapon is a weapon of mass destruction. An effective attack using a chemical or biological agent can easily kill thousands of people.

Chemical Weapons


A chemical weapon is any weapon that uses a manufactured chemical to kill people. The first chemical weapon used effectively in battle was chlorine gas, which burns and destroys lung tissue. Chlorine is not an exotic chemical. Most municipal water systems use it today to kill bacteria. It is easy to manufacture from common table salt. In World War I, the German army released tons of the gas to create a cloud that the wind carried toward the enemy.

Modern chemical weapons tend to focus on agents with much greater killing power, meaning that it takes a lot less of the chemical to kill the same number of people. Many of them use the sorts of chemicals found in insecticides. When you spray your lawn or garden with a chemical to control aphids, you are, in essence, waging a chemical war on aphids.

Many of us tend to imagine a chemical weapon as a bomb or missile that releases highly toxic chemicals over a city. (For example, the movie "The Rock" featured a scenario in which terrorists tried to launch a missile loaded with the chemical VX, a nerve toxin.) But in 1995, the group Aum Shinrikyo released sarin gas, a nerve gas, in the Tokyo subway. Thousands were wounded and 12 people were killed. No giant bombs or missiles were involved -- the terrorists used small exploding canisters to release the gas in the subway.

Although the attack wasn't intentional, Blackwater Worldwide, contracted by the U.S. to protect officials in Iraq, accidentally dropped canisters of CS, a gas similar to tear gas, on soldiers and civilians at a checkpoint to clear the road for a convoy in 2005 [source: Risen].

Biological Weapons

A biological weapon uses a bacteria or virus, or in some cases toxins that come directly from bacteria, to kill people. If you were to dump a load of manure or human waste into a town's well, that would be a simple form of biological warfare -- human and animal manure contain bacteria that are deadly in a variety of ways. In the 19th century, American Indians were infected with smallpox through donated blankets.

A modern biological weapon would use a strain of bacteria or a virus that would kill thousands of people. Tom Clancy has explored the idea of biological terrorism in two books: "Executive Orders" and "Rainbow Six." In both books, the source of infection is the Ebola virus. In these plot lines, the infection is spread through small aerosol cans (like those used by insecticide products to create "bug bombs") released at conventions, or through misting systems used to cool sports venues.

Feared Chemical Agents

Firefighters help one another remove hazardous material protective suits to avoid self-contamination after responding to a simulated chemical attack during an anti-terrorism force protection exercise.
Lance Cpl. Edward Brown/U.S. Marine Corps

An effective chemical attack would use chemicals that are extremely toxic to people in small quantities. From least to most threatening, the most commonly feared agents are:

  • Sarin -- Sarin is a nerve agent. Once inside your body, nerve agents affect the signaling mechanism that nerve cells use to communicate with one another. Sarin is a cholinesterase inhibitor -- it gums up the cholinesterase enzyme, which your nerve cells use to clear themselves of acetylcholine. When a nerve cell needs to send a message to another nerve cell (for example, to cause a muscle to contract), it sends the message with the acetylcholine. Without cholinesterase to clear the acetylcholine, muscles start to contract uncontrollably -- this eventually causes death by suffocation since the diaphragm is a muscle. It acts in five to 12 hours [source: Keyes]. It is not particularly difficult to manufacture, and if you were trapped in a one-cubic-meter closet with 100 milligrams of sarin in the air, inhaling it would kill you in 1 minute [source: Keyes].
  • Cyclosarin -- Cyclosarin is another nerve agent. It works in the same way as sarin, but it is more than twice as toxic. You'd only need to be in the cubic-meter closet with 35 milligrams of airborne cyclosarin to die in 1 minute [source: Ellison]. Saddam Hussein's Iraq made cyclosarin during the Gulf War [source: Tucker].
  • Soman -- Soman is also like sarin, but it acts faster, in 40 seconds to 10 minutes [source: Keyes]. It's about as toxic as cyclosarin [source: Ellison]. The Soviet Union stockpiled soman in the 1960s [source: Tucker].
  • VX -- VX works in the same way as sarin, but it is a liquid, while sarin vaporizes. It is also ten times more toxic than sarin. Ten milligrams on the skin will kill a person [source: Keyes]. A sticky version exists that adheres to whatever it falls on [source: Harrison]. The United States made VX during the 1950s and 1960s [source: Tucker].
  • Novichoks -- Novichoks are nerve agents. To make them, two ordinary chemicals are mixed to form a toxic product. As recently as 1990, at least three novichoks existed (novichok-5, novichok-#, and novichok-7), but whether large quantities exist today is unknown. All novichok agents are more toxic than VX. Some may be up to 10 times more toxic [source: Stewart]. They may also work differently than the nerve agents listed here, possibly rendering existing antidotes ineffective. The Soviet Union began making novichoks in the 1980s [source: Tucker]. In Russian, novichok means "newcomer."

Not all feared chemical weapons attack the nerves. Blistering agents, like mustard gas, blister the skin, destroy lung tissue and can kill people. But they are less deadly than nerve agents.


One of the problems with these chemical agents is that there is no easy way to protect yourself. On the battlefield, soldiers wear gas masks and complete skin coverings when chemical or biological attack is deemed possible. If a city were to experience a large-scale VX attack, people would have to be wearing a waterproof and airtight suit and a gas mask at the time of the attack in order to be protected.

Feared Biological Agents

As indicated by the maculopapular rash covering his entire body, this young boy contracted smallpox. The photo was taken in Bangladesh in 1974.
Jean Roy/CDC

There are many ways to implement a biological attack, but these are some of the most feared agents, from least to most threatening:

  • Ebola virus -- The virus takes about a week to kill the victim, and it spreads through direct contact. The Marburg virus is just as deadly.
  • Botulinum toxin -- Clostridium botulinum bacteria produce the botulinum toxin, and this toxin is deadly to people in incredibly small quantities (as little as a billionth of a gram). The toxin inhibits the release of the chemicals in nerve cells that cause muscle contractions, so it causes paralysis.
  • Tularemia -- Bacteria cause tularemia. The most deadly forms, which cause fever or respiratory illness, kill 5 to 7 percent of people, but vaccines are an effective prevention, and antibiotics can clear the infections [source: Britannica].
  • Pneumonic plague -- Plague is caused by a bacterium. In pneumonic plague, bacteria infest the lungs, and a person dies in three to four days if not treated. Pneumonic plague is also contagious, spreading through coughing and sneezing. The most recent pandemic, which lasted until 1922, killed 10 million people. Eventually, public health measures drove the bacteria's hosts, rodents and fleas, out of cities, and antibiotics became available [source: Britannica]. But even today, antibiotics must be delivered fast to prevent death from pneumonic plague. Plague is a weapon. Japan may have released infected fleas in China during World War II, and the United States and Soviet Union found ways to aerosolize the bacteria during the Cold War [source: Britannica].
  • Anthrax -- A bacterium causes anthrax. It has a spore form that is very durable. If the spores or bacteria get into your lungs, they reproduce and create a toxin that can be fatal. See "How Anthrax Works" for more information.
  • Smallpox -- Smallpox is a virus. It was a major killer until it was controlled with vaccinations in the 20th century. It has been eradicated worldwide, but the fear is that terrorists could release new strains. The main problem with smallpox, unlike with anthrax, is that it is highly contagious. It spreads and kills very quickly. Up to 40 percent of people who catch the virus die from it in about two weeks, and there is no good treatment for the disease. Vaccinations are the main protection, but they must be given prior to infection in order to work.

It would also be possible to cause significant problems by targeting the food supply. For example, foot-and-mouth disease has been a huge problem in Europe. Spreading the disease to the United States would be relatively easy and very disruptive.


The Spread of Biological and Chemical Agents

The previous sections listed 11 of the most-feared chemical and biological agents. There are dozens of others that aren't as well known, either because they are not as toxic or not as easy to spread.

There are three ways to spread a chemical or biological agent so that it would infect a large number of people:


  • Through the air
  • Through a municipal water supply
  • Through the food supply

The most-feared scenario is through the air. Here are the techniques most commonly discussed:

  • A bomb or a missile explodes, spreading the chemical or biological agent over a wide area.
  • A crop-duster or other aircraft sprays the agent over a city.
  • A car or truck drives through the city spraying a fine mist along city streets in crowded areas.
  • Small bombs or aerosol canisters are released in crowded areas like subways, sports arenas or convention centers.

Here are some ways the U.S. is protecting civilians against attacks:

Chemical and biological weapons are huge, ever-changing subjects. To learn more about them, follow the links on the next page.

Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Burns, John. "'Chemical Ali' Gets Death Sentence." The New York Times. June 24, 2007. (8/27/2009)
  • Chivers, C.J. "Threats and responses: The Kurds; Still Suffering From '88 Gas Attack, a Village
  • Chyba, Christopher. "Russia's Poison Gases." The New York Times. October 20, 2002. (8/27/2009)
  • Cohen, Roger. "Roger Cohen: A U.S.-Iranian Conversation." The New York Times. November 10, 2008. (8/27/2009)
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