Carcinogen Health Dictionary

Any agent capable of causing cancer. Chemicals are the largest group of carcinogens. Major types include polycyclic aromatic hydrocarbons (PAHs), which occur in tobacco smoke, pitch, tar fumes, and soot. Exposure to PAHs may lead to cancer of the respiratory system or skin. Certain aromatic amines used in the chemical and rubber industries may cause bladder cancer after prolonged exposure.

The best-known physical carcinogen is high-energy radiation, such as nuclear radiation and X-rays. Exposure may cause cancerous changes in cells, especially in cells that divide quickly: for example, changes in the precursors of white blood cells in the bone marrow causes leukaemia. The risk depends on the dosage and duration of exposure. Over many years, exposure to ultraviolet radiation in sunlight can cause skin cancer. Another known physical carcinogen is asbestos (see asbestos-related diseases).

Only a few biological agents are known to cause cancer in humans.

SCHISTOSOMA HAEMATOBIUM, one of the blood flukes responsible for schistosomiasis, can cause cancer of the bladder; and ASPERGILLUS FLAVUS, a fungus that produces the poison aflatoxin in stored peanuts and grain, is believed to cause liver cancer.

Viruses associated with cancer include strains of the human papilloma virus, which are linked to cancer of the cervix; the hepatitis B virus, which is linked to liver cancer; and a type of herpes virus which is associated with Kaposi’s sarcoma.

A chemical or other agent that has been implicated in causing cancer.

n. any substance that, when exposed to living tissue, may cause the production of cancer. Known carcinogens include ionizing radiation and many chemicals, e.g. those found in cigarette smoke and those produced in certain industries. They cause damage to the DNA of cells that may persist if the cell divides before the damage is repaired. Damaged cells may subsequently develop into a *cancer (see also carcinogenesis). An inherent susceptibility to cancer may be necessary for a carcinogen to promote the development of cancer. See also oncogenic. —carcinogenic adj.