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Chemical and biological weapons are organisms, toxins, and chemicals used to cause death or harm through their poisonous properties. Alongside nuclear weapons, biological and chemical weapons are weapons of mass destruction because they can kill or injure large numbers of people and cause environmental damage.

Countries have used biological and chemical weapons in warfare and assassinations. They have killed more than 100,000 people and injured more than one million since World War I. But countries have also cooperated with the goal to ban them.

Several organizations conduct detailed studies on countries’ activities on biological and chemical weapons. This page brings this research together to present which and how many countries have pursued, possessed, or used these weapons recently and historically. It also looks at which countries have joined the international treaties that seek to eliminate them.

All our interactive charts on Biological and Chemical Weapons