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What are the Leading Causes of Lung Cancer?


Updated October 02, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: What are the Leading Causes of Lung Cancer?

When we talk about the leading causes of lung cancer, our thoughts jump to smoking. But while some of the leading causes are obvious, others important causes may surprise you. Are you familiar with these causes?


Smoking is responsible for 80 to 90% of lung cancers, and causes roughly 160,000 cancer deaths each year in the United States. That said, 10% of men and 20% of women who develop lung cancer have never smoked, and over half of lung cancers related to smoking occur in former, not current, smokers.


Exposure to radon gas in our homes is the second leading cause of lung cancer overall, responsible for 21,000 lung cancer deaths each year. Radon exposure is the number one cause of lung cancer in non-smokers.

Radon gas results from the natural decay in uranium beneath our homes, and can enter our homes through cracks in the foundation, openings around drains, and gaps around pipes. Elevated levels of radon have been found in homes in all 50 states and throughout the world. Since radon is an invisible, odorless gas, the only way to know if you are at risk is to test your home for radon.

Secondhand Smoke

The third leading cause of lung cancer, responsible for over 3,000 deaths each year in people who have never smoked, is secondhand smoke. Living with someone who smokes raises your risk of developing lung cancer by 20 to 30%, and even brief exposures can cause the damage that can lead to lung cancer.

Occupational Exposures

On-the-job exposure to cancer-causing substances is responsible for 6 to 17% of lung cancers in men in the United States. Some of the culprits include diesel fumes, organic solvents such as benzene, chemicals such as vinyl chloride, and metals such as chromium and arsenic. Employers are required to provide information sheets about hazardous substances you may be exposed to, and it is important to check these out and take any recommended precautions.

Air Pollution

Air pollution generated from traffic, the combustion of diesel fuel, coal, and wood is responsible for around 5% of lung cancer in men, and 3% in women in the United States. In some areas of the world, these numbers are significantly higher.

Other Causes and Possible Causes of Lung Cancer


American Cancer Society. Secondhand Smoke. Updated 11/09/10. http://www.cancer.org/Cancer/CancerCauses/TobaccoCancer/secondhand-smoke

Centers for Disease Control and Prevention. Lung Cancer. Risk Factors. Updated 12/14/11. http://www.cdc.gov/cancer/lung/basic_info/risk_factors.htm

Centers for Disease Control and Prevention. Occupational Cancer. Updated 02/02/12. http://www.cdc.gov/niosh/topics/cancer/

Grant, W. Air pollution in relation to U.S. cancer mortality rates: an ecological study; likely role of carbonaceous aerosols and polycyclic aromatic hydrocarbons. Anticancer Research. 2009. 29(9):3537-45.

National Cancer Institute. Secondhand Smoke and Cancer. Updated 01/12/11. http://www.cancer.gov/cancertopics/factsheet/Tobacco/ETS

United States Environmental Protection Agency. Radon. Health Risks. Updated 09/30/10. http://www.epa.gov/radon/healthrisks.html

Robinson, C. et al. Occupational lung cancer in US women. 1984-1998. American Journal of Industrial Medicine. 2011. 54(2):102-17.

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