Unlike some cancers, doctors know what causes lung cancer.
Smoking
Cigarette smoking is the number one cause of lung cancer. Ninety percent of lung cancer cases occur in people who smoke. The more cigarettes you smoke, the higher your risk of developing lung cancer. Cigarette smoke contains over 4,000 chemicals, many of which are proven to be cancer-causing substances called carcinogens. Carcinogens cause irreversible damage to your body's DNA cells and increase the chance of cancerous change.
Radon Inhalation
Radon is a gas not detected by sight, taste, or smell. Radon is the second most common cause of lung cancer. Radon gas causes between 15,000 and 22,000 lung cancer deaths each year in the United States. Radon gas comes up through the soil and in through cracks in your home or a building's foundation. It tends to build up in unventilated basements, pipes, drains, or walls. Home sales in many places now require radon testing - call the Environmental Protection Agency (EPA) or the National Environmental Health Association for more info.
Workplace Chemicals
People (mine workers, pipe fitters, and shipbuilders) who are exposed to certain workplace materials, such as asbestos, (see the sidebar “When the culprit is fibers, not nicotine”) have a higher risk of lung cancer because inhaled fibers and dust can become embedded in the lung cells, causing a chronic inflammatory reaction that can eventually result in cancerous cell changes. Workers' risks are much higher if they smoke in addition to having these types of chemical exposures.
Secondhand Smoke
The EPA has classified secondhand smoke as a known cause of cancer in humans. Secondhand smoke is also known as environmental tobacco smoke and is classified as any mixture of smoke given off by the burning end of a cigarette, cigar, pipe, or smoke exhaled from a smoker's lungs. Secondhand smoke causes approximately 3,400 lung cancer deaths in the U.S. every year. Some of the carcinogens in secondhand smoke include formaldehyde, benzene, vinyl chloride, arsenic, ammonia, and hydrogen cyanide. These agents have an immediate effect on your cardiovascular system.
Age
As with many cancers, your risk for developing lung cancer increases with age. The longer you smoke and the more cigarettes you smoke, the greater your chances of developing lung cancer. Less than 1 percent of lung cancer cases occur in people under age 40. The development of lung cancer increase thereafter, with the average patient age at diagnosis around 60.
Family History
People who have a first-degree relative (mother, father, brother, or sister) with lung cancer have a higher incidence of lung cancer because some lung cancer is linked to mutations in the genetic cells that can be passed on to blood relatives.
