By Charlie Keenan

UN weapons inspectors uncover parts of a 122-mm chemical warhead in Iraq. This slide was used by U.S. Secretary of State Colin Powell during a presentation before the UN Security Council in early February.
(Photo Courtesy U.S. Department of State)

Nuclear, chemical, or biological weapons are weapons of mass destruction because they can kill many people.

The U.S., China, and Russia all have weapons of mass destruction, but these countries have agreements with each other not to use the weapons.

Countries like Iraq and North Korea, however, are believed to have or to be developing these weapons as well. These countries are not trusted to contain their weapons. The UN and the U.S. are worried that these weapons could find their way into the hands of dictators and possibly terrorists. Iraq has used chemical weapons on its own people and is believed to have hidden vast supplies of them. North Korea backed out of a weapons containment treaty and has started developing the material needed to build nuclear bombs.

"Too little attention has been paid to these issues over the last 10 years," says Ted Turner, co-chairman of the Nuclear Threat Initiative, an organization that is trying to get people to notice the danger of weapons of mass destruction.

Turner—a billionaire philanthropist—says the time to do something about it is now. "If we are to reduce the threat from nuclear, biological, and chemical weapons in all its forms, we need to raise public awareness and inspire leadership and cooperation in this country and throughout the world."

Here is a brief overview of weapons of mass destruction:

Nuclear weapons. These are the most powerful and destructive explosives ever made. They can be delivered by airplane or missile. Modern nuclear bombs can have the power of several million tons of TNT—about 8 to 40 times more explosive than the bombs that were dropped on Japan in 1945. The United States has been the only country to use nuclear weapons in combat, dropping bombs on Hiroshima and Nagasaki. The Japanese surrendered, ending World War II in the Pacific.

Chemical weapons. These are made up of poisonous compounds. They can be fired in artillery shells that explode in the air, or dropped from airplanes. They cause harm through skin contact, inhalation, eating contaminated food, or drinking tainted water. Chemical weapons attack body surfaces or the central nervous system.

Mustard gas, for example, is usually in the form of tiny droplets that are spread through the air. It damages any surface it contacts, such as the skin, eyes, and lungs. Nerve agents can shut down the body's nervous system. VX is one of the most powerful of these, but many other nerve agents can cause death within minutes after exposure. Chemical weapons were used extensively in World War I, and also in the Iran-Iraq War (1980-1988). Terrorists used the nerve agent sarin in an attack in a Tokyo subway in 1995.

Biological weapons. These include bacteria, viruses, fungi, and other living microorganisms that can kill. Like chemical weapons, biological weapons can be dropped by airplane or fired in artillery shells. Because these weapons are alive, they are hard to control once released. This is one reason why biological weapons have rarely been used. Microorganisms can reproduce, making an environment more dangerous over time. The only large military attacks were in the 1930s and 1940s, when the Japanese dumped plague and other bacteria from airplanes over China. Anthrax, a bacterium that occurs naturally in soil, was used in attacks through the U.S. mail system in 2001.