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How do environmental factors contribute to cancer risk?
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cancer
View through an endoscope of a polyp, a benign precancerous growth projecting from the inner lining of the colon.
Environmental factors are significant contributors to cancer risk, with the majority of cancers linked to extrinsic influences rather than heredity. These factors generally act as carcinogens—agents that interfere with normal cellular function, often by damaging DNA, which can lead to uncontrolled cell growth and tumor formation.1234
Carcinogens are categorized into three primary types:
- Chemicals: This includes substances found in tobacco smoke, industrial pollutants, and certain dietary sources like processed meats or foods cooked at high temperatures. Some chemicals act as initiators that cause permanent DNA damage, while others act as promoters that stimulate the replication of abnormal cells.1345
- Radiant Energy: Both ultraviolet (UV) rays from sunlight and ionizing radiation (such as X-rays or radioactive materials) can damage biological macromolecules and DNA, increasing the risk of cancers like melanoma or leukemia.674
- Oncogenic Viruses: Certain infectious agents, such as human papillomavirus (HPV) and hepatitis B and C, are linked to specific cancers.24
Because these factors are largely external, many cancers are considered preventable through lifestyle improvements, such as maintaining a healthy diet, increasing physical activity, and avoiding known carcinogens.24