Holden Comprehensive Cancer Center
Carcinogens and How They Are Brought to Light
Peer Review Status: Holden Comprehensive Cancer Center, Cancer Information Service
Cancer is caused by a cell's genetic blueprint being abnormal. This abnormality could be inherited from relatives or it could be caused by exposures to substances outside the body, such as radiation chemicals or viruses. These substances that can cause changes to the cell are called carcinogens. Carcinogen and carcinogenic refer to a substance that causes cancer. Carcinogens do not cause cancer in every case, every time. Substances classified as carcinogens may have different levels of cancer-causing ability. Some might cause cancer only after a very long exposure at high concentration. The risk for developing cancer depends on many factors, which includes the length and intensity of exposure to the carcinogen and the person's genetic makeup.
How do we know if something is a carcinogen?
Scientists combine the data from both types of studies to make a well-studied estimate about a substance's ability to cause cancer. If the evidence is conclusive, the substance may be considered a probable carcinogen.
The most widely used system for classifying carcinogens comes from the International Agency for Research on Cancer (IARC). IARC is part of the World Health Organization and has evaluated the cancer-causing ability of about 900 substances in the past 30 years. These substances are then placed into one of 5 groups:
In the United States, the National Toxicology Program (NTP) releases the Report on Carcinogens every two years. The NTP is formed from several government groups, including the National Institutes of Health, the Centers for Disease Control and Prevention and the Food and Drug Administration.
The Report on Carcinogens identifies two groups of substances:
Points to remember about these lists:
Last modification date:
Mon Aug 7 13:09:57 2006