A carcinogen is a substance that is capable of causing cancer in humans or animals. If a substance is known to promote or aggravate cancer, but not necessarily cause cancer, it may also be called a carcinogen. Though there are many things that are believed to cause cancer, a substance is only considered carcinogenic if there is significant evidence of its carcinogenicity.
A carcinogen may act on deoxyribonucleic acid (DNA), causing dangerous changes, or it may work to increase the rate of cell division. This change in cell division may work to increase the probability of DNA changes. Some carcinogens promote the development of cancer in other ways as well.
It is important to note that carcinogens don’t lead to cancer after every exposure. Some cause cancerous changes following high-level, prolonged exposure, while others may cause damage at lower levels and shorter exposure periods. Furthermore, an individual’s unique genetic makeup may influence the body’s response to a carcinogen.
Testing human subjects for carcinogenic behavior and properties is considered unethical, not to mention hazardous to the health of the test subjects. As such, animals are often used for carcinogen testing. Additionally, cell cultures from both humans and animals are used in testing. Scientists also consider the effects of substances at the molecular level in determining whether or not they are carcinogenic. Evidence of links between exposure to substances and the development of cancer is also considered.