Risk Factors

Research has found several risk factors for lung cancer.¹ A risk factor is anything (for example, a behavior or a characteristic) that increases the chance of getting a disease. Different risk factors change risk by different amounts.

Examples of risk factors for lung cancer include—

• Smoking tobacco and being around others' smoke.
• Exposures at home or work (such as radon gas or asbestos).
• Personal history (such as having radiation therapy or a family history of lung cancer).

We know a lot about risk factors, but they don't tell us everything. Some people who get cancer don't seem to have any known risk factors. Other people have one or more risk factors and do not get cancer. If a person has several risk factors and develops lung cancer, we don’t know how much each risk factor contributed to the cancer.

Smoking and Secondhand Smoke

Cigarette smoking is the number one risk factor for lung cancer.^{2 3} In the United States, cigarette smoking causes about 90% of lung cancers.² Tobacco smoke is a toxic mix of more than 7,000 chemicals.^{3 4} Many are poisons. At least 70 are known to cause cancer in people or animals. People who smoke are 15 to 30 times more likely to get lung cancer or die from lung cancer than people who do not smoke. Even smoking a few cigarettes a day or smoking occasionally increases the risk of lung cancer. The more years a person smokes and the more cigarettes smoked each day, the more risk goes up.^{1 2 3}

People who quit smoking have a lower risk of lung cancer than if they had continued to smoke, but their risk is higher than the risk for people who never smoked.^{2 5 6} Quitting smoking at any age can lower the risk of lung cancer.^{2 5 6} For help quitting, visit Quit Smoking or call 1-800-QUIT-NOW (1-800-784-8669); TTY 1-800-332-8615.

Smoking can cause cancer almost anywhere in the body. Smoking causes cancer of the mouth, nose, throat, voicebox (larynx), esophagus, bladder, kidney, pancreas, cervix, stomach, blood, and bone marrow (acute myeloid leukemia).^{2 3}

More information about cigarette smoking and lung cancer is available in CDC's Smoking and Tobacco Use fact sheets, the 2010 Surgeon General's Report, the 2004 Surgeon General's Report, and the National Cancer Institute's Cigarette Smoking and Cancer: Questions and Answers.

Using other tobacco products such as cigars or pipes also increases the risk for lung cancer.^{3 7} For more information, visit Tobacco Industry and Products fact sheets and Questions and Answers About Cigar Smoking and Cancer.

Smoke from other people's cigarettes, pipes, or cigars (secondhand smoke) also causes lung cancer.^{3 4 8 9 10} When a person breathes in secondhand smoke, it is like he or she is smoking. Two out of five adults who don't smoke and half of children in the United States are exposed to secondhand smoke.¹¹ Every year in the United States, about 3,000 people who never smoked die from lung cancer due to secondhand smoke.^{8 9 10}

Exposures at Home and Work That May Cause Lung Cancer

Several exposures in the home or workplace may cause lung cancer—^{1 12}

• Radon is a naturally occurring gas that comes from rocks and dirt and can get trapped in houses and buildings.^{13 14} It cannot be seen, tasted, or smelled. According to the U.S. Environmental Protection Agency (EPA), radon causes about 20,000 cases of lung cancer each year, making it the second leading cause of lung cancer.^{14 15} Nearly one out of every 15 homes in the U.S. is estimated to have high radon levels.¹⁶ The EPA recommends testing homes for radon and using proven methods to reduce high radon levels. For more information, visit A Citizen's Guide to Radon.
• Examples of substances found at some workplaces that increase risk include asbestos, arsenic, diesel exhaust, and some forms of silica and chromium.^{1 12 17 18} For many of these substances, the risk of getting lung cancer is even higher for those who also smoke.³

For more information on carcinogens and cancer in the workplace, visit the links below.

• Agency for Toxic Substances and Disease Registry ToxFAQs™
• National Toxicology Program's 11th Report on Carcinogens
• National Institute for Occupational Safety and Health

Family History

Risk of lung cancer may be higher if a person's parents, siblings (brothers or sisters), or children have had lung cancer.^{1 19 20} This increased risk could come from one or more things. They may share behaviors, like smoking. They may live in the same place where there are carcinogens such as radon. They may have inherited increased risk in their genes. For more information, visit CDC's National Office of Public Health Genomics.

Radiation Therapy to the Chest

Cancer survivors who had radiation therapy to the chest are at higher risk of lung cancer.²¹ Patients at highest risk include those treated for Hodgkin disease and women with breast cancer treated with radiation after a mastectomy (but not a lumpectomy).

Diet

Scientists are studying many different foods and dietary supplements to see whether they increase the risk of getting lung cancer. There is much we still need to know. We do know that smokers who take beta-carotene supplements have increased risk of lung cancer.²² For more information, visit NCI's Diet and Cancer and Lung Cancer Prevention.

Also, arsenic in drinking water (primarily from private wells) can increase the risk of lung cancer.²² For more information, visit the EPA's Arsenic in Drinking Water.