Types of Carcinogens

  • Carcinogens can be substances, radionuclides, or radiation that promote the formation of cancer.
  • Radioactive substances like gamma rays and alpha particles are considered carcinogens due to the radiation they emit.
  • Non-radioactive carcinogens include inhaled asbestos, certain dioxins, and tobacco smoke.
  • Carcinogenicity can arise from both natural and synthetic substances.
  • Activation-dependent carcinogens require metabolic activation or modification to induce cancer, while activation-independent ones do not.

Classification of Carcinogens

  • International Agency for Research on Cancer (IARC): Established in 1965, part of the World Health Organization, based in Lyon, France, classifies agents into 5 groups.
  • Globally Harmonized System (GHS): United Nations initiative that harmonizes different systems of assessing chemical risk, classifies carcinogens into 2 categories.
  • U.S. National Toxicology Program (NTP): Mandated to produce a biennial Report on Carcinogens, classifies carcinogens into 2 groups.
  • American Conference of Governmental Industrial Hygienists (ACGIH): Private organization that publishes threshold limit values (TLVs) for occupational exposure, classifies carcinogens into 5 groups.

Carcinogens in Specific Cancers

  • Breast cancer: Elevated blood levels of estrogen contribute to breast carcinogenesis, estrogen metabolism can lead to the formation of genotoxic, mutagenic carcinogens.
  • Colon cancer: Tobacco smoke may be responsible for up to 20% of colorectal cancers in the United States, bile acids induce DNA damage in colon cells.
  • Stomach cancer: Helicobacter pylori infection is the main causative factor, infection increases production of reactive oxygen species (ROS) in gastric epithelial cells.

Carcinogens in Food, Tobacco, and Environmental Exposure

  • Carcinogens in Food and Beverages: Burnt foods, N-nitrosamines, alcohol consumption, bile acids, and Helicobacter pylori infection have been linked to cancer.
  • Carcinogens in Tobacco and Smoking: Cigarette smoking, marijuana smoke, secondhand smoke exposure, and toxicants in tobacco smoke contribute to cancer development.
  • Carcinogens in Environmental Exposure: Certain metals, CMR substances, occupational exposure, and specific occupations like shiftwork, painting, and firefighting increase cancer risk.
  • Carcinogens in Hormonal Factors: Estrogen exposure, estrogen metabolites, estrogen quinones, and alcohol intake have been associated with an increased risk of breast cancer.
  • Carcinogens in DNA Damage: Unrepaired DNA damage, DNA adducts, estrogen exposure, age-related accumulation of DNA damage, and bile acids contribute to cancer development.

Additional Concepts

  • History of cancer, mutagen, possible carcinogen, safe handling of carcinogens, teratogen are related concepts.
  • References to scientific articles and studies on carcinogens and cancer risk.

Carcinogen Mentions

Carcinogen Data Sources

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