Just like a nuclear bomb , a chemical or biological weapon is a weapon of mass destruction that can easily kill thousands of people in a single attack efficiently.
A chemical weapon is any weapon that uses a chemical compound produced to kill people. The first chemical weapon used in battle was chlorine gas , which burns and destroys the tissues of the lungs . Chlorine products are easy to find. Most municipal water treatment systems currently uses chlorine to kill bacteria and is very easy to produce it from the salt. In World War I, the German army released tons of this gas to undermine the enemy.
Modern chemical weapons usually focus on agents that are much more lethal meaning that a much smaller amount of chemical is required to kill the same number of people. Many of them use chemicals found in insecticides . Basically, when you sprinkle a chemical in the garden or on the grass to control insects, is "waging a chemical war" against them.
Many tend to imagine a chemical weapon as a bomb or a missile that releases highly toxic compounds on a city (for example, in the movie "The Rock", terrorists tried to launch a missile loaded with the compound VX , a toxin that attacks the nervous system) . But in 1995, the group Aum Shinrikyo released sarin gas (which acts on the nervous system) in the Tokyo subway. Thousands were injured and 12 people died without there any bomb or missile giant involved. All we needed was the terrorists of small bombs that explode and liberassem gas in the subway.
A biological weapon uses bacteria , viruses or toxins in some cases from bacteria. If manure or human waste were thrown into a pit of a small town, it would be, quite simply, a form of biological warfare, as human and animal wastes contain bacteria that can cause several problems, including death. In the nineteenth century, Native Americans were infected with smallpox through donated blankets.
A modern bioweapon would use a type of bacteria or virus with the power to affect or kill thousands of people. Tom Clancy, for example, explored the idea of biological terrorism in two of his books: "Executive Orders" and "Rainbow 6". In both, the source of infection is the Ebola virus.