Lung Cancer Risk Factors

A risk factor is anything that increases a person’s chance of getting a disease such as cancer.

Factors that may affect lung cancer risk

Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.

But having a risk factor, or even several, does not mean that you will get the disease. And some people who get the disease may have few or no known risk factors.

Several risk factors can make you more likely to develop lung cancer. These factors are related to the risk of lung cancer in general.

Risk factors you can change

Tobacco smoke

Smoking is by far the leading risk factor for lung cancer. About 80% of lung cancer deaths are thought to result from smoking, and this number is probably even higher for small cell lung cancer (SCLC). It’s rare for someone who has never smoked to have SCLC.

The risk of lung cancer for people who smoke is many times higher than for people who don’t smoke. The longer you smoke and the more packs a day you smoke, the greater your risk.

Cigar smoking, pipe smoking, and menthol cigarette smoking are almost as likely to cause lung cancer as cigarette smoking. Smoking low-tar or “light” cigarettes increases lung cancer risk as much as regular cigarettes.

Secondhand smoke

If you don’t smoke, breathing in the smoke of others (called secondhand smoke or environmental tobacco smoke) can increase your risk of developing lung cancer. Secondhand smoke is the third most common cause of lung cancer in the United States.

If you or someone you care about needs help quitting, see How to Quit Using Tobacco  or call the American Cancer Society at 1-800-227-2345

Exposure to radon

Radon is a naturally occurring radioactive gas that results from the breakdown of uranium in soil and rocks. You can’t see, taste, or smell it. According to the US Environmental Protection Agency (EPA), radon is the second-leading cause of lung cancer in the United States, and it’s the leading cause among people who don’t smoke.

Outdoors, there is so little radon that it is not likely to be dangerous. But indoors, radon can be more concentrated. Breathing it in exposes your lungs to small amounts of radon. This may increase a person’s risk of lung cancer.

Homes and other buildings in nearly any part of the country can have high indoor radon levels (especially in basements).

For more information, see Radon and Cancer.

Exposure to asbestos

People who work with asbestos (such as in mines, mills, textile plants, places where insulation is used, and shipyards) are several times more likely to die of lung cancer. Lung cancer risk is much greater in workers exposed to asbestos who also smoke. It’s not clear how much low-level or short-term exposure to asbestos might raise lung cancer risk.

People exposed to large amounts of asbestos also have a greater risk of developing mesothelioma, a type of cancer that starts in the pleura (the lining surrounding the lungs). For more on this type of cancer, see Mesothelioma.

In recent years, government regulations have greatly reduced the use of asbestos in commercial and industrial products. It’s still present in many homes and other older buildings, but it’s not usually considered harmful as long as it’s not released into the air by deterioration, demolition, or renovation. For more information, see Asbestos and Cancer Risk.

Exposure to other cancer-causing agents in the workplace

Other carcinogens (cancer-causing agents) found in some workplaces that can increase lung cancer risk include:

• Radioactive ores, such as uranium
• Inhaled chemicals, such as arsenic, beryllium, cadmium, silica, vinyl chloride, nickel compounds, chromium compounds, coal products, mustard gas, and chloromethyl ethers
• Diesel exhaust

The government and industry have taken steps in recent years to help protect workers from many of these exposures. But the dangers are still there, so if you work around these agents, be careful to limit your exposure whenever possible.

Taking certain dietary supplements

Studies looking at the possible role of vitamin supplements in reducing lung cancer risk have had disappointing results. In fact, multiple studies found that people who smoked and took beta-carotene supplements actually had an increased risk of lung cancer. The results of these studies suggest that people should avoid taking beta-carotene supplements.

Arsenic in drinking water

Studies of people in parts of Southeast Asia and South America with high levels of arsenic in their drinking water have found a higher risk of lung cancer. In most of these studies, the levels of arsenic in the water were many times higher than those typically seen in the United States, even areas where arsenic levels are above normal. For most Americans who are on public water systems, drinking water is not a major source of arsenic.

Risk factors you cannot change

Previous radiation therapy to the lungs

People who have had radiation therapy to the chest for other cancers are at higher risk for lung cancer, particularly if they smoke. Examples include people who have been treated for Hodgkin lymphoma  or women who were treated with chest radiation for breast cancer.

Air pollution

In cities, air pollution, such as from diesel exhaust, appears to raise the risk of lung cancer slightly. This risk is far less than the risk caused by smoking, but about 1% to 2% of all deaths from lung cancer in the United States are thought to be due to outdoor air pollution.

Personal or family history of lung cancer

If you have had lung cancer, you have a higher risk of developing another lung cancer.

Brothers, sisters, and children of people who have had lung cancer may have a slightly higher risk of lung cancer themselves, especially if the relative was diagnosed at a younger age. It’s not clear how much of this risk might be due to shared genes among family members and how much might be from shared household exposures (such as tobacco smoke or radon).

Researchers have found that genetics do play a role in some families with a strong history of lung cancer. (To learn more, see What Causes Lung Cancer?)

Factors with uncertain or unproven effects on lung cancer risk

Smoking marijuana

There are reasons to think smoking marijuana might increase lung cancer risk.

• Marijuana smoke contains tar and many of the same cancer-causing substances that are in tobacco smoke. (Tar is the sticky, solid material that remains after burning, which is thought to contain most of the harmful substances in smoke.)
• Marijuana cigarettes (joints) are typically smoked all the way to the end, where tar content is the highest.
• Marijuana is inhaled very deeply, and the smoke is held in the lungs for a long time, which gives any cancer-causing substances more opportunity to deposit in the lungs.
• Because marijuana is still illegal in many places, it may not be possible to control what other substances it might contain.

It’s been hard to study whether there is a link between marijuana and lung cancer because marijuana has been illegal in many places for so long, and it’s not easy to gather information about the use of illegal drugs. Also, in studies that have looked at past marijuana use in people who had lung cancer, most of the people who smoked marijuana also smoked cigarettes. This can make it hard to know how much any increased risk is from tobacco and how much might be from marijuana. We do know that smoking marijuana will irritate your lungs and possibly increase your risk of getting more lung infections. More research is needed to know the cancer risks from smoking marijuana.

E-cigarettes

E-cigarettes are a type of electronic nicotine delivery system. Most e-cigarettes contain nicotine, so the Food and Drug Administration (FDA) classifies them as “tobacco products.”  The FDA states that e-cigarettes cause health risks, including lung damage. Furthermore, e-cigarettes have not been shown to improve your chances of quitting smoking. Whether e-cigarettes directly increase your risk of lung cancer is not yet known.