Smoking is the number one cause of lung cancer. It causes about 87 percent of lung cancer cases. Tobacco smoke contains many chemicals that are known to cause cancer. And smokers are not the only ones affected. Nonsmokers can breathe in secondhand smoke and get lung cancer or other illnesses.
Radon exposure is the second leading cause of lung cancer. Radon is a colorless, odorless radioactive gas that occurs naturally in soil. It comes up through the soil and enters buildings through small gaps and cracks. One out of every 15 homes in the U.S. has a radon problem.
Industrial exposures pose a lung cancer risk. Working with certain hazardous materials, such as asbestos, uranium, arsenic, cadmium, chromium, nickel, and some petroleum products is especially dangerous.
Genetic factors also play a role in the likelihood that someone gets lung cancer. Mutations in several genes have been linked to lung cancer, suggesting the disease has a genetic component. So a family history of lung cancer may indicate a higher risk of developing the disease.