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How Biological and Chemical Warfare Works
by Marshall Brain

During the gulf war, the threat of Iraqi chemical and biological weapons felt very real, because it was known that Iraq had done extensive research on these weapons. In the wake of the September 11 terrorist attacks, the threat feels very real again. A chemical or biological weapon used in a large city would kill thousands of people.

In this edition of HowStuffWorks, you will learn how chemical and biological weapons really work, how they might be deployed and what the actual threats are.

Understanding Warfare
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, 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 -- 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 nations like Iraq, don't pay attention to significant international treaties. 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 neurotoxin, in the Tokyo subway. Thousands were wounded and 12 people were killed. No giant bombs or missiles were involved -- the terrorists used small exploding cannisters to release the gas in the subway.

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 or 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
An effective chemical attack would use chemicals that are extremely toxic to people in small quantities. The most commonly feared agents include:

  • Sarin - Sarin is a nerve agent. This means that, once inside your body, it affects 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, which eventually causes death by suffocation (since the diaphragm is a muscle).

    Sarin is probably the most feared chemical agent because it has actually been used by terrorists to kill people. In 1995, the group Aum Shinrikyo released sarin gas in the Tokyo subway, wounding thousands and killing 12 people. It is not particularly difficult to manufacture, and about 1 milligram in the lungs will kill a person.

  • VX - VX is very similar to Sarin. It works in the same way, but is more toxic. One milligram on the skin will kill a person. See this page for more information.

  • Mustard Gas - Mustard gas has been around since World War I. It blisters the skin and destroys lung tissue. About 10 milligrams in the lungs will kill a person.

  • Lewisite - Lewisite, like mustard gas, is a blistering agent, and has also been around since World War I.

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

  • Anthrax - Anthrax is a bacteria, but 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 world-wide, 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. This page has extensive information.

  • Botulin toxin - Botulin bacteria produce the botulin 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.

  • Ebola virus - The Ebola virus was popularized as a biological warfare agent by two books written by Tom Clancy. The virus takes about a week to kill the victim, and spreads through direct contact.
It would also be possible to cause significant problems by targeting the food supply. For example, foot-and-mouth disease has recently been a huge problem in Europe. Spreading the disease to the United States would be relatively easy and very disruptive.

The Spread
The previous sections listed eight of the most-feared chemical and biological agents. There are dozens of others that are less 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.
To learn more about toxic agents, how they're spread and methods the military uses to protect soldiers against them, check out the links on the next page.

Lots More Information

Related HowStuffWorks Articles

Other Informative Links


Gas Masks

Protective Clothing


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