Poisons and Toxins (Encyclopedia of Science)
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 serious bodily harmven death. In a large quantity, then, water could be classified as a poison.
The term toxicity is used to express how poisonous a chemical is. Scientists distinguish between two kinds of toxicity: acute and chronic. Acute toxicity refers to the amount of damage caused by a chemical after a short-term exposure to a large dose of the chemical. For example, a person might accidentally swallow a tablespoon of rat poison. The effects caused by that accident would be described as the chemical's acute toxicity.
Scientists have various ways of measuring the acute toxicity of a chemical. Perhaps the most common is called LD50. The abbreviation LD50 stands for "lethal dose, 50 percent." It is the amount of the chemical...
(The entire section is 1120 words.)
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