carcinogens

Carcinogens are agents that can contribute to cancer development by initiating or promoting malignant transformation in cells. They include chemical substances, physical factors such as ionizing and ultraviolet radiation, and certain biological agents that increase cancer risk after exposure.

Most cancers arise after long-term exposure to one or more carcinogens, with risk influenced by dose, duration, and individual susceptibility, including genetics, age, and overall health. Mechanisms involve DNA damage and mutations in oncogenes and tumor suppressor genes, chromosomal instability, and epigenetic alterations. Inflammation, immune modulation, and hormonal effects can also contribute to tumor development and progression.

Examples of chemical carcinogens include polycyclic aromatic hydrocarbons from tobacco smoke and environmental pollution, aflatoxins produced by certain fungi, nitrosamines in processed foods, benzene, formaldehyde, and asbestos. Physical carcinogens include ultraviolet radiation from sun exposure and ionizing radiation from medical sources or radon. Biological carcinogens include certain viruses such as human papillomavirus (HPV), hepatitis B and C viruses, and Epstein-Barr virus, as well as some bacteria associated with chronic inflammation.

Carcinogens are evaluated by international and national health bodies. The International Agency for Research on Cancer (IARC) classifies agents into groups ranging from Group 1 (carcinogenic to humans) to Group 4 (probably not carcinogenic). Regulatory agencies translate these assessments into exposure limits, labeling, and safety measures to reduce risk, especially in workplaces and consumer products.

Prevention focuses on reducing exposure, adopting protective practices, vaccination against HPV and hepatitis B where appropriate, and cancer screening programs to detect disease early and lower mortality.