Chemical spills are any accidental releases of synthetic chemicals that pose a risk to the environment.

Spills occur at any of the steps between the production of a chemical and its use. A railroad tank car may spring a leak; a pipe in a manufacturing plant may break; or an underground storage tank may corrode allowing its contents to escape into groundwater. These spills are often classified into four general categories: the release of a substance into a body of water; the release of a liquid on land; the release of a solid on land; and the release of a gas into the atmosphere. The purpose of this method of classification is to provide the basis for a systematic approach to the control of any type of chemical spill.

Some of the most famous chemical spills in history illustrate these general categories. For example, seven cars...