Clinical Definition

A carcinogen is an agent or substance that may damage cellular DNA or alter cell metabolism, and, in so doing, potentially lead to the development of cancer. Carcinogens are classified according to their carcinogenicity.

In Our Own Words

A carcinogen is something believed to contribute to the development of cancer. Usually, a carcinogen either causes a cell to divide too quickly or too haphazardly, or in some other way it leads to changes in the DNA imprint of a cell.

Not all carcinogens have the same potential to cause cancer. Various government agencies, such as the Environmental Protection Agency, classify carcinogens depending on how likely they are to lead to cancer. For instance, certain carcinogens (cigarette smoke or formaldehyde, for instance) require long-term exposure before they cause cancer.