Lung cancer risk factors include smoking, air pollution, exposure to toxins, and a family history of lung cancer. Understanding these risk factors may help people reduce their chances of developing lung cancer.

Risk factors are things that increase the chances of a person developing a condition. However, they do not predict who will or will not develop a disease.

This article looks at the risk factors for lung cancer and how to reduce their impact. It then looks at lung cancer symptoms, diagnosis, and treatment.

According to the American Cancer Society, the main risk factors for lung cancer are:

Some of these risk factors, such as a person’s family history, are fixed. This means a person cannot change them. However, eliminating risk factors that are not fixed can help a person lower their risk of developing lung cancer.

Having risk factors does not necessarily mean an individual will get lung cancer. Similarly, it is possible for people with no apparent risk factors to develop lung cancer.

Currently, it is unclear whether the following factors affect a person’s lung cancer risk:

According to the Centers for Disease Control and Prevention (CDC), tobacco smoke contributes to 80–90% of all lung cancer cases, making it the leading risk factor for lung cancer.

This percentage may be higher for small cell lung cancer (SCLC) because this type of cancer is extremely rare in people who never smoke.

People who smoke are 15–30 times more likely to develop lung cancer than those who do not. The longer and more frequently a person smokes, the greater the risk.

Secondhand smoke

People who do not smoke but breathe in the smoke from others are also at an increased risk of lung cancer.

Secondhand smoke is the third most common risk factor for lung cancer, responsible for an estimated 3,000 deaths from lung cancer each year.

Find 11 tips for quitting smoking here.

Air pollution occurs when harmful particles and gases enter the air people breathe. It is prevalent in urban and densely populated areas.

According to an older study in Thorax, experts estimate that air pollution may be responsible for 712,000 deaths worldwide each year, with 62,000 of those being the result of lung cancer. However, more research is necessary to determine if these estimates are correct.

Several types of radiation exposure can increase the risk of lung cancer. They include:

Radon exposure

Radon is one of the leading causes of lung cancer for people who do not smoke. It is responsible for around 21,000 lung cancer deaths per year.

Radon is a naturally occurring gas. Outside, it is unlikely to endanger people. Indoors, radon can be more concentrated. Long-term radon exposure indoors can lead to lung cancer.

Radiation therapy

People undergo radiation therapy as a treatment for cancer. However, radiation therapy on the chest can increase the risk for lung cancer. This could affect people undergoing radiation therapy for breast cancer, for example.

In many cases, this risk is unavoidable, as the benefits of radiation therapy for people with other types of cancer typically outweigh the risks.

Other sources of radiation people may come into contact with include radioactive ores, such as uranium.

Asbestos is a naturally occurring mineral that is carcinogenic, or cancer-causing. Before doctors understood its dangers, people used asbestos as a material in construction, car manufacturing, and industrial settings.

Breathing in asbestos increases the risk of both lung cancer and malignant mesothelioma, a type of cancer that affects the lungs’ lining. The risk is especially high if a person becomes exposed to asbestos and also smokes.

Other carcinogens may pose a risk for people who regularly come into contact with them. This may affect people who work with dangerous substances, such as:

  • arsenic
  • cadmium
  • beryllium
  • silica
  • vinyl chloride
  • nickel compounds
  • chromium compounds
  • coal products
  • mustard gas
  • chloromethyl ethers

Close family members of individuals diagnosed with lung cancer have a 50% higher risk of developing lung cancer themselves. This is true across sexes, races, and ethnicities, and it is not affected by other risk factors.

People are also more likely to get lung cancer again if they have had it previously.

It is not always possible to prevent lung cancer. Some risk factors, such as previous radiation exposure and family history, cannot be changed.

However, some of the most significant risk factors are avoidable. People can reduce their risk of lung cancer by:

  • Stopping smoking: According to the CDC, people who stop smoking halve their risk of developing cancer within 10 years of quitting. As such, it is never too late to stop smoking. People can find free resources for quitting smoking at
  • Avoiding secondhand smoke: If someone in the household smokes, ask them to go outside so that others do not inhale the smoke. Keep cars and other enclosed spaces smoke free.
  • Testing the home for carcinogens: The Environmental Protection Agency (EPA) recommends that everyone tests their home for radon. People can learn about finding radon testing on their website. People can also test their drinking water for arsenic or cadmium.
  • Avoiding carcinogens at work: Check whether substances could be carcinogenic and follow health and safety guidelines when working with them. The Occupational Safety and Health Administration (OSHA) provides advice on what to do if a company is not following these guidelines.
  • Improving indoor air quality: It is not always possible to avoid air pollution outdoors, but people can do things to improve indoor air quality. This includes removing any sources of carcinogens, such as smoke and open fires, and improving ventilation. Seek professional guidance on removing or containing asbestos.

People in high-risk groups for lung cancer can also get an annual screening. This helps to detect signs of cancer early, which improves the chances of successful treatment.

Lung cancer develops when abnormal cells grow in a disorganized fashion, forming malignant tumors and damaging the surrounding tissue.

Toxins from tobacco and other environmental risk factors contribute to this by damaging cell DNA, which changes how the cells behave.

There are two primary types of lung cancer:

Non-small cell lung cancer (NSCLC)

This is the most common type of lung cancer, accounting for 80–85% of all cases. The main subtypes include:

Adenosquamous carcinoma and sarcomatoid carcinoma are less common subtypes.


SCLC accounts for around 10–15% of lung cancers. Unfortunately, this type grows and spreads quickly. Among individuals with SCLC, 70% have cancer that has spread to other parts of the body by the time doctors make a diagnosis.

Because there are few nerve endings in the lungs, cancer may not cause any pain. Symptoms may only appear when the disease progresses.

Potential symptoms include:

  • a persistent cough that worsens over time
  • coughing up blood or rust-colored phlegm
  • hoarseness
  • chest pain that gets worse while coughing, breathing deeply, or laughing
  • shortness of breath or wheezing
  • frequent chest infections
  • unexplained weight loss and tiredness

People should seek a doctor’s advice if they notice any of these symptoms.

Lung cancer treatment can vary depending on the type and severity of the cancer. Doctors may treat NSCLC with a combination of:

  • surgery to remove tumors
  • chemotherapy drugs to shrink or kill cancerous cells
  • radiation therapy
  • targeted therapy drugs to block the growth and spread of cancer

Individuals with SCLC typically receive either radiation therapy and chemotherapy, or radiation with or without immunotherapy. As SCLC often spreads to other parts of the body, surgery may not be helpful.

The primary lung cancer risk factors are smoking and exposure to secondhand smoke, radon, air pollution, and other carcinogens. A personal or family history of lung cancer also raises the risk.

People can mitigate the risk of developing lung cancer by stopping smoking, addressing environmental concerns such as radon and asbestos, and keeping the home and other enclosed spaces free from cancer-causing substances wherever possible.