Cancer causing agents or carcinogens are chemicals or substances that lead to the development of cancer in human being and other animals. A cancer causing agent is also known as a carcinogen which could be any substance that may be directly or indirectly involved in causing cancer or spreading cancer.
A carcinogen could be any substance like a chemical, radionuclide or even harmful radioactive radiations that alter the DNA and alter the genome of the living being. Genes are responsible for the proper functioning of the metabolic processes and get cells in tune. Any alterations in these genomes can lead to cells which do not function as they are intended to and lead to cells which grow uncontrollably and cause cancer. Carcinogens effect the DNA by deleting specific base pairs that interfere with the body’s functioning. Cancer is the condition of the body’s cells to grow uncontrollably and do not under go apoptosis which is also known as a programmed cell death. In normal circumstances the cells whose DNA is damaged beyond repair is killed. But not in cancerous cells, here the cells with damaged DNA grow uncontrollably and lead to formation of tumors and slowly replace the healthy cells of the body.
Carcinogens can be of natural and artificial origin. They are also classified based on chemical, radiation and biological. Some of the natural carcinogens known to man are Aflatoxin B1. This I produced by the fungi Aspergillus Flavus. Many viruses like Rous Sarcoma Virus and Hepatitis B produce substances that alter the human genome beyond repair. Artificial man made carcinogens are asbestos, tobacco, dioxins like kepone, benzene and other list of chemicals produced by man. This list is slowly increasing to include new substances which are used regularly without the knowledge of them being carcinogenic. Ultra violet and gama rays are non chemical carcinogenic substances.