cancer
Risk Factors for Cancer
Environmental factors
Numerous environmental factors increase the risk of developing cancer. Tobacco smoke contains carcinogens that substantially increase the risk of developing cancers of the lungs, mouth, throat, esophagus, kidneys, and bladder. Pollutants in the air or water, such as asbestos, industrial waste, or cigarette smoke, can increase the cancer risk. Many chemicals are known to cause cancer, and many others are suspected of doing so. For example, asbestos exposure may cause lung cancer and Mesothelioma (cancer of the pleura). Exposure to pesticides is associated with a higher risk of some types of cancer (for example, Sources of Radiation Exposure is a risk factor for the development of cancer. Extended exposure to ultraviolet radiation, primarily from sunlight, causes skin cancers. Ionizing radiation is carcinogenic. X-rays (including computed tomography [CT]) use ionizing radiation, and people who have many tests have a small increased risk of cancer (see also Exposure to the radioactive gas radon, which is released from soil, increases the risk of lung cancer. Normally, radon disperses rapidly into the atmosphere and causes no harm. However, when a building is placed on soil with a high radon content, radon can accumulate within the building, sometimes causing levels in the air that are sufficiently high enough to cause harm. Radon is breathed into the lungs, where it may eventually cause lung cancer. In exposed people who also smoke, the risk of lung cancer is further increased. Many other substances have been investigated as possible causes of cancer, but more study is needed to identify those chemicals that increase the risk of cancer. 