Radiation is the process by which energy travels through space and objects in the form of waves. Natural radiation includes cosmic rays in outer space and rays emitted naturally from the human body, rocks (such as granite), and isotopes in water. In addition, there are artificially created radiation, such as X-rays, isotopes, etc.. If these rays reach a certain intensity, they can interfere with the normal function of cells, destroy the structure of cells, and even cause changes in the genetic material of cells. If the cells are damaged and cannot be repaired normally, instead of dying, they may mutate and form into cancer cells. Therefore, for example, decades after the atomic bombing of Hiroshima and Nagasaki in Japan in 1945, the incidence of leukemia, breast cancer, stomach cancer, multiple myeloma, and urinary tract tumors increased significantly. The incidence of thyroid cancer also increased rapidly after the Chernobyl nuclear accident in the former Soviet Union. The 2011 earthquake in Japan may have also increased the incidence of cancer in people exposed to nuclear radiation in nearby areas. This is especially true for thyroid cancer because of the large amount of 131I released, as they tend to accumulate in the thyroid gland. In addition to nuclear radiation, ultraviolet light is also carcinogenic, so those who are exposed to the sun for a long time, such as seafarers, have a higher incidence of skin cancer. In addition, some people who are engaged in some special occupations and have special radiation exposure may also have special tumors, such as miners in uranium and tin mines have higher incidence of lung cancer due to their long-term exposure to radon and radon daughters.