Physical agents can be produced as a result of nuclear accidents, ionising radiation (X-Rays), non-ionising radiation (UV ultraviolate radiation) and radon gas (radioactive gas found in in the earth’s soil and rocks that contain uranium).
People can come into contact with chemical agents when working with certain industrial chemicals. Doses and exposure periods to agents will determine the likelihood of developing the disease. There are some carcinogenic substances such as: asbestos, arsenic, benzene, cadmium, mercury, nickel, lead, chlorinated hydrocarbons, and naphthylamine.
As for biological carcinogens, it is estimated that 18% of cancers are related to infectious disease (virus, bacteria or parasites). Such is the case with human papillomavirus (HPV) and uterine neck cancer, hepatitis B, and liver cancer, as well as Helicobacter pylori and stomach cancer.