Causes of Lung Cancer

Smoking causes an estimated 87 to 90 percent of lung cancer cases. Smokers who quit (even after smoking for years) greatly reduce their risk of lung cancer. However, the risk remains. A powerful reminder of this was the death in 2005 of ABC television's news anchor Peter Jennings, a former smoker, from lung cancer. But even nonsmokers can die of lung cancer, as did Dana Reeve, the wife of actor Christopher Reeve.

Research suggests that cigarette smoking leads to lung cancer at least in part because the body converts a substance in cigarette smoke, benzo[a]pyrene diol epoxide (BPDE), into a potent carcinogen. In addition, several comprehensive reports have concluded that passive smoking—inhaling the smoke from cigarettes smoked by others—also can cause lung cancer.

Substantial evidence supports this conclusion about passive smoking. Carcinogens are present in side-stream smoke emerging from the end of a burning cigarette. Cigarette smoke particles persist in the homes of smokers. Tobacco-smoke components can be detected in the body fluids of nonsmokers exposed to passive smoking. In addition, nonsmokers have a 20 to 30 percent greater chance of developing lung cancer if they are exposed to secondhand smoke at home or work. Taking into account the projected deaths from lung cancer and cardiovascular disease, some studies suggest that passive smoking is one of the leading causes of preventable deaths in this country.

Exposure to toxic substances like radon and asbestos also can lead to lung cancer. Radon is estimated to be the leading cause of lung cancer among nonsmokers and the second leading cause of the disease overall. Radon is a colorless, odorless gas formed naturally during the decay of uranium found in rocks and soil. Radon in the soil can pollute the air of a home by entering through cracks or other openings, usually in the basement. The incidence of lung cancer caused by radon is highest among miners, who are often exposed to high levels. Most people who die of radon-associated cancer, according to the U.S. National Cancer Institute, were also smokers.

Asbestos is a fibrous mineral that was used in building materials until the 1980s. Chronic exposure to asbestos can cause both lung cancer and mesothelioma—a cancer involving the pleura (the membranes that cover the lungs). The combination of asbestos exposure and cigarette smoking is especially dangerous.

Air pollution, including traffic fumes and smokestack emissions, also may contribute to lung cancer.

Publication Review By: Peter B. Terry, M.D., M.A.

Published: 14 Sep 2011

Last Modified: 14 Sep 2011