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What Causes Lung Cancer?


Updated June 06, 2014

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

Young woman smoking in morning
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Question: What Causes Lung Cancer?

Though we know that smoking causes lung cancer, lung cancer is a multifactorial disease –- that is, many factors work together to either cause or prevent cancer. Between 80 and 90% of lung cancers are due to smoking, yet 10% of men and 20% of women who develop the disease have never smoked. On the other side of the equation, many people who smoke do not develop lung cancer.

Causes of lung cancer may be additive, or in certain cases, more than additive. Individuals who are exposed to asbestos and smoke, or exposed to radon and smoke, have a higher risk of developing lung cancer than can be explained by the risk of these causes added together. On the other hand, certain dietary practices and exercise may reduce the risk of some of these causes. What causes lung cancer?


Smoking is responsible for 87% of lung cancers overall. Cigar smoking raises the risk as well, as most likely does the use of marijuana.


Radon is the leading cause of lung cancer in non-smokers, and the second most common cause of lung cancer overall.

Secondhand Smoke

Secondhand smoke is responsible for roughly 3,000 lung cancer deaths per year in the United States. Living with someone who smokes raises your risk of developing lung cancer by 20-30%.

Environmental Causes

Environmental causes of lung cancer include exposure to chemicals, wood smoke, and radiation. In one study, air pollution was estimated to be the cause of lung cancer in 5% of men and 3% of women in the United States.

Occupational Causes

Occupational causes of lung cancer include exposure to chromium, tar, arsenic, and nickel, among other substances. In the U.S., it’s estimated that 13 to 29% of lung cancers in men are related to occupational exposures.


Genetic factors can play a role in lung cancer, and 1.7% of lung cancers are considered “hereditary.” An inherited predisposition to lung cancer is more common in women, non-smokers, and patients under the age of 60 who develop the disease.

Possible Causes of Lung Cancer

Researchers are looking at other factors that may play a role in the development of lung cancer. Infections, such as human papillomavirus (HPV), may increase risk, but as of now we don’t know if it plays a causative role. Exposure to radon via granite countertops is a current area of controversy in which the jury is still out. An excess intake of alcohol may also act along with other risk factors to increase the risk of developing lung cancer.

Thankfully, many of these causes of lung cancer are preventable. In addition, a healthy diet and exercise appear to lower the risk.

As a last note, while it is important to understand the causes of lung cancer so we can better understand ways to prevent it, people living with lung cancer don’t need us to judge how they may have “caused” their cancer. They need our unconditional caring and support. Many cancers and diseases are related to unhealthy behaviors, but we don’t seem to judge people with other conditions as harshly. We need to understand the causes of lung cancer without adding to the stigma of lung cancer.


Environmental Protection Agency. Radon. Health Risks. Updated 03/11/10. http://www.epa.gov/radon/healthrisks.html

National Cancer Institute. Lung Cancer Prevention (PDQ). Health Professional Version. Evidence of Benefit. Updated 08/06/09. http://www.cancer.gov/cancertopics/pdq/prevention/lung/HealthProfessional/page4

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