Carcinogens promote cancer or increase it's propagation. It could be a substance, radionuclide (atom w/ unstable nucleus)
or radiation. These carcinogens have the ability to damage the genome or disrupt the cellular metabolic process. Several
radioactive substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example
gamma rays and alpha particles, which they emit. Inhaled asbestos, certain dioxins, and tobacco smoke are common carcinogens.
Aflatoxin B1, which is produced by the fungus Aspergillus flavus growing on stored grains, nuts and peanut butter, is an
example of a potent, naturally-occurring microbial carcinogen.