The top risk factor for developing lung cancer is smoking, according to the Centers for Disease Control and Prevention. Exposure to radon, a chemical that occurs naturally in dirt and rocks and sometimes becomes trapped inside homes, is the second-leading cause of lung cancer in the United States. Exposure to secondhand smoke is another significant cause of lung cancer and lung cancer deaths. Cancer survivors who once had radiation therapy to their chests are also at higher risk.
Occupational exposure to toxic chemicals such as arsenic and nickel is another risk factor in the development of lung cancer, as is prolonged exposure to aromatic hydrocarbons or ether, explains eMedicineHealth. A history of chronic obstructive pulmonary disease also increases the risk of developing lung cancer by up to six times, while exposure to asbestos increases the risk about nine times. Many experts also believe that exposure to air pollution increases the risk of developing lung cancer as much as exposure to secondhand smoke.
The term "neoplasm" refers to a tumor in which cell growth is abnormal or uncontrolled, according to the Free Dictionary. Not all neoplasms are cancerous; some are nonmalignant, or benign.
The most common causes of benign lung neoplasms is inflammation, either from an infection or another cause, notes WebMD. Fungal infections, such as aspergillosis and histoplasmosis; tuberculosis; and certain types of pneumonia are common causes of this type of growth. Rheumatoid arthritis and sarcoidosis, an inflammatory disease that affects multiple organs, sometimes cause benign lung tumors as well.