Lung cancer risk factors: smoking, radon and what you can change

What lung cancer is

Lung cancer forms in the tissues of the lung, usually in the cells that line the air passages. It is the leading cause of cancer death in both men and women. The two main types are small cell and non-small cell lung cancer; non-small cell is the more common type (MedlinePlus) (NCI PDQ).

Risk factors that raise the risk

The National Cancer Institute (NCI) lists these risk factors (NCI PDQ):

• Cigarette, cigar and pipe smoking. Tobacco smoking is the most important risk factor. It causes about 9 out of 10 cases of lung cancer in men and about 8 out of 10 in women. People who smoke have about 20 times the risk of people who do not, and the risk grows with the number of cigarettes a day and the number of years smoked. Low tar or low nicotine cigarettes do not lower the risk (NCI PDQ).
• Secondhand smoke. Breathing in smoke from someone else's cigarette or other tobacco product exposes you to the same cancer-causing agents as smokers, in smaller amounts (NCI PDQ) (MedlinePlus).
• Family history. People with a relative who has had lung cancer may be twice as likely to get it. Because smoking and secondhand smoke also run in families, it is hard to know how much of this comes from the family history itself (NCI PDQ).
• HIV infection. People with HIV may have more than twice the risk. Smoking rates are higher in people with HIV, so it is not clear how much comes from the infection and how much from smoking (NCI PDQ).
• Radon. Radon is a radioactive gas from the breakdown of uranium in rocks and soil. It can enter homes through cracks in floors, walls or the foundation and build up over time. High radon levels at home or work raise the number of lung cancer cases and deaths, and the risk is higher in smokers. In people who have never smoked, about 26% of lung cancer deaths have been linked to radon (NCI PDQ).
• Other radiation. Radiation therapy to the chest (for example for breast cancer or Hodgkin lymphoma), imaging tests such as CT scans, and atomic bomb radiation. For radiation therapy, the higher the dose, the higher the risk (NCI PDQ).
• Workplace exposures. Asbestos, arsenic, chromium, nickel, beryllium, cadmium, and tar and soot. These can cause lung cancer even in people who have never smoked, and the risk goes up with the level of exposure and is higher again in people who also smoke (NCI PDQ).
• Air pollution. Living in areas with higher levels of air pollution raises the risk (NCI PDQ) (MedlinePlus).
• Beta carotene supplements in heavy smokers. Beta carotene pills raise the risk, especially in people who smoke one or more packs a day, and more so in those who also have at least one alcoholic drink every day (NCI PDQ).

Smoking is also the main risk factor for COPD (NHLBI); see COPD risk factors.

Which ones you can change

What lowers the risk

• Not smoking. NCI calls this the best way to prevent lung cancer (NCI PDQ).
• Quitting. After 10 years without smoking, the risk of lung cancer drops by 30% to 60%. How much depends on how long and how much a person smoked and how long ago they quit. The risk never gets as low as in people who never smoked (NCI PDQ). Counseling, nicotine replacement products and antidepressant therapy have helped people quit for good (NCI PDQ).
• Less radon. Lowering radon levels may lower the risk, especially in people who smoke (NCI PDQ).
• Less workplace exposure. Laws that limit worker exposure to asbestos, arsenic, nickel and chromium, and laws against smoking at work, may help lower the risk (NCI PDQ).

NCI says it is not clear whether a diet high in fruits and vegetables or being physically active lowers the risk, because smokers tend to differ on both. Beta carotene pills in people who do not smoke and vitamin E supplements do not lower the risk (NCI PDQ).

Symptoms to report

Lung cancer may not cause signs or symptoms until it is advanced. When there are symptoms, MedlinePlus lists (MedlinePlus):

• Chest pain or discomfort
• A cough that does not go away or gets worse over time
• Coughing up blood
• Trouble breathing, wheezing or hoarseness
• Loss of appetite, weight loss for no known reason, or feeling very tired
• Trouble swallowing, or swelling in the face or the veins of the neck

Tell your provider about any of these. They have other causes too, and only tests can tell.

Who is eligible for screening

Because lung cancer often has no symptoms early, screening matters for people at high risk. The US Preventive Services Task Force recommends a low-dose CT scan every year for adults aged 50 to 80 who have a 20 pack-year smoking history and who smoke now or quit within the past 15 years (USPSTF 2021). The lung cancer screening eligibility check works out your pack-years. The lung cancer risk calculator estimates a 6-year risk for people who have smoked, the COPD screening check covers the other big smoking-related lung disease, and screening tests by age lists the other checks for your age.

Common questions

Can people who never smoked get lung cancer?

Yes. Radon, secondhand smoke, workplace exposures such as asbestos, air pollution and family history all raise the risk without smoking. In people who never smoked, about 26% of lung cancer deaths have been linked to radon (NCI PDQ).

Is it too late to quit if I have smoked for years?

No. Quitting lowers the risk, and after 10 years the risk is 30% to 60% lower (NCI PDQ). If you quit within the past 15 years and meet the age and pack-year limits, you may still qualify for screening (USPSTF 2021).