Home > Encyclopedia of Science > Poisons and Toxins

• Toxicity
• Words to Know
• LD50 Value for Various Chemicals
• Some naturally occurring poisons
• Poisons produced by human technology

A poison is any chemical that kills or injures an organism. The term toxin refers to a poison produced by a living organism, such as a microorganism, a plant, or an animal. In everyday practice, the terms poison and toxin are often used interchangeably.

It is important to understand that any chemical is potentially poisonous. All that is required for a chemical to cause toxicity is a dose large enough to cause some harmful effect. For example, water could be considered toxic if a person drank four gallons of it all at once. In such a case, the water would cause...