Radiation is a well-known exogenous source of cancer risk. There are two primary types: ionizing and non-ionizing radiation. Ionizing radiation, such as X-rays and gamma rays, can cause direct damage to DNA, leading to mutations and cancer. The most notable example is the increased risk of leukemia and thyroid cancer following exposure to high levels of ionizing radiation, such as those from nuclear accidents. On the other hand, ultraviolet (UV) radiation from the sun is a type of non-ionizing radiation that predominantly contributes to skin cancers, including melanoma.
