Carcinogens are cancer causing agents, they carry out their effect by altering cellular metabolism or damaging DNA directly in cells , which interferes with biological processes, and induces the uncontrolled, malignant division, ultimately leading to the formation of tumors. They can either be radiation or radionuclide, non- radiation carcinogens and natural carcinogenic agents.

NATURAL CARCINOGENIC AGENTS: These are carcinogens which are produced naturally they include
a. AFLATOXIN B1 : This is produced by molds called fungus Aspergillus flavus which grow in soil, decaying vegetation, hay, and grains. They are regularly found in improperly stored staple commodities such as cassava , chili peppers, corn, cotton seed, millet , peanuts , rice , sesame seeds , sorghum , sunflower seeds , tree nuts ,
wheat , and a variety of spices. High-level of aflatoxin can result in carcinoma of the liver thus the food containing aflatoxin must be avoided.
b.HUMAN PAPILLOMA VIRUS(HPV). HPV is the most common sexually transmitted infection globally. This includes genital warts and precancerous lessons.
Nearly all cervical cancer is due to HPV making it as of the most carcinogenic agents known to humans.

c.HEPATITIS B is the inflammation of the liver caused by hepatitis B virus(HBV). Hepatitis B virus is the most virulent out of the hepatitis infections. It is transmitted by contamination with the infected fluids especially through sexual intercourse
HBV can result in result in cirrhosis and liver cancer may eventually develop.Others organism which are known to be carcinogenic are Helicobacter pylori, helminths and Clonorchis sinensis.

RADIATION OR RADIONUCLIDE(RADIOACTIVE NUCLIDE)
High exposure to radiation are known to be carcinogenic, high-energy radiation ultraviolet radiation (present in sunlight), x-ray and gamma radiation is generally carcinogenic.ultraviolet radiation is d most common cause of skin cancer.
Some irradiated food products are also known to carcinogenic.

NON-RADIATION RADIATION CARCINOGENS
a. TOBACCO: A large number of known potent carcinogens are found in cigarette , this includes polycyclic aromatic hydrocarbons (PAH),Benzene and Nitrosamine. This may increase the risk of lung cancer in smokers
b. DIOXIN AND DIOXIN-LIKE COMPOUNDS. These are one of the major chemical substances extensively used by humans they can be found in paints, herbicides and various chemicals.
Dioxins have been considered highly toxic and able to cause reproductive and developmental problems, damage the immune system, interfere with hormones and also cause cancer.
c. PREPARED FOODS: Chemicals used in processed and cured meat such as some brands of bacon and sausages may produce carcinogens.Bisphenol found in canned foods has been shown to cause cancer in humans.

http://www.banixhealthcare.com/carcinogens/