Lung Cancer Risk Factors - Smoking and Much More

Known, Probable, and Possible Causes of Lung Cancer

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A comprehensive list of the many risk factors for lung cancer.

When you think about the risk factors for lung cancer, it's likely that smoking is your first thought. But there are many factors in addition to smoking that are known to cause, or possibly contribute to, the development of lung cancer.

Importance of Knowing the Risk Factors for Lung Cancer

Why is it important to be aware of these risk? There are a few reasons.  

  • Prevention - Having the knowledge that a substance such as radon or an occupational chemical, or a practice such as smoking raises risk, people may have a better opportunity to avoid that risk, and
  • Early Detection - Using this knowledge of risk factors - including those not commonly known - people at risk for lung cancer may have a heightened awareness. This awareness, in turn, may help people educate themselves about the earliest symptoms of lung cancer, as well as having the opportunity to undergo lung cancer screening if this is felt to be appropriate. The current criteria for screening are discussed at the bottom of this article, but based on other risk factors, you and your doctor may wish to consider screening outside of these guidelines.

Known, Probable, and Possible Risk Factors for Lung Cancer

Before listing risk factors for lung cancer, it's important to note that some risk factors for lung cancer are quite clear, whereas others are considered only a probability or a possibility. Some practices that are common, such as smoking, are easier to study than other less common exposure.

It's also important to make a distinction between causation and correlation. Just because 2 things are correlated, it doesn't necessarily mean there is causation. An example commonly used to make the distinction between a real cause and a random association is the link between ice cream and drowning.

More ice cream is consumed in summer, and there are more drownings in summer. This means there is a correlation between ice cream and drowning but does not mean that ice cream causes drowning. 


Smoking is responsible for at least 80 percent of lung cancer deaths in the United States. Although cigar smoking is less dangerous than cigarette smoking, those who inhale cigar smoke are 11 times more likely than non-smokers to develop lung cancer.


Age is an important risk factor for lung cancer, as lung cancer becomes more common with increasing age. That said, young adults and sometimes even children may develop lung cancer.


Exposure to radon in the home is the second leading cause of lung cancer and the leading cause in non-smokers. Radon is an odorless colorless gas that enters homes through cracks in solid foundations, construction joints, cracks in walls, gaps in suspended floors, gaps around service pipes, cavities inside walls, and the water supply.

As such, exposure to radon is a serious health threat to children and nonsmoking men and women and may occur in their own homes. Found in homes in all 50 states and worldwide, the only way to know if you are at risk is to have your home tested.

Secondhand Smoke

Secondhand smoke raises the risk of lung cancer for nearby nonsmokers by 20 percent to 30 percent and is responsible for roughly 7,000 cases of lung cancer each year in the United States. On the other hand, a large prospective cohort study published recently in the Journal of the National Cancer Institute of more than 76,000 women confirmed a strong association between cigarette smoking and lung cancer but found no link between the disease and secondhand smoke.

Air Pollution

Both indoor and outdoor air pollution can raise the risk of lung cancer. Outdoor pollution may seem like an obvious cause, but Indoor pollution from the use of coal for cooking and heating is also an important risk factor.

Occupational and Household Chemicals

Exposure to chemicals and substances on-the-job, such as formaldehyde and asbestos, silica, chromium, is an important risk factor for lung cancer, especially when combined with smoking.

Occupation Exposure

Many work setting may expose workers to carcinogens, leading to an increased risk of lung and other cancers. For example, crystalline silica and chrysotile asbestos are well-known human carcinogens; as expected, workers exposed to silica dust and asbestos fiber are at a higher risk of developing lung cancer. Uranium miners and nuclear plant workers are also known to have an increased lung cancer risk.

Genetic Risk Factors

It has been noted for many years that lung cancer appears to run in some families. More recently it's been found that people with several hereditary gene mutations (mutations present at birth) are more likely to develop lung cancer.


Radiation - primary x-radiation and gamma radiation in the form of radiotherapy, diagnostic radiation, and environmental background radiation, is a risk factor for lung cancer. People who have radiation therapy to the chest for cancers such as Hodgkin's disease (a type of lymphoma) or following a mastectomy for breast cancer have an increased risk of developing lung cancer. Radiation therapy after a lumpectomy for breast cancer does not appear to increase risk. The risk is higher when radiation is received at a younger age and can vary depending upon the dose of radiation received.

Lung Diseases  

Even though COPD (chronic obstructive pulmonary disease) and lung cancer are both caused by smoking, COPD and asthma appear to be an independent risk factor for lung cancer. It's felt that pulmonary fibrosis increases the risk of lung cancer by 40 percent, and tuberculosis is also considered a risk factor for lung cancer.

Medical Conditions 

People with certain cancers appear to have an increased risk of lung cancer (whether due to genetic causes, common exposures, or treatments such as radiation.) These include Hodgkin's disease, non-Hodgkin's lymphoma, testicular cancer, uterine sarcoma, head and neck cancers, esophageal cancer, bladder cancer, chronic lymphocytic leukemia, cervical cancer, and kidney cancer. In addition, people with HIV, autoimmune diseases such as rheumatoid arthritis, and organ transplant recipients also have an increased risk of developing lung cancer.

Diet and Food Supplements

Cured meat (eg. sausage, pressed duck, cured pork, etc.) deep fried cooking and chili have been associated with an increased lung cancer risk. Although some studies indicate carotenoids decrease lung cancer risk, results have been ambiguous, and some have even indicated that high-dose supplements of vitamin A can be harmful.


From a pooled analysis of 7 prospective and 3137 lung cancer cases, a slightly greater risk of lung cancer was indicated among people who consumed at least 30 g/day of alcohol.

Lung Cancer Screening

Currently, lung cancer screening is recommended for people who are between the ages of 55 and 80, who have at least a 30 pack-year history of smoking, and continue to smoke, or quit smoking, in the past 15 years. Depending on the presence of other risk factors, you and your doctor may consider lung cancer screening outside of these guidelines. For example, if you have been exposed to high levels of radon, had radiation therapy for lymphoma in your 20’s, and have COPD, your risk of developing lung cancer may be high even if you have never smoked. If you have some of these risk factors you may wish to print off this article to bring with you to your doctor. At the current time, roughly 40 percent of people are initially diagnosed when lung cancer has already progressed to stage 4 – a stage at which curative surgery is not possible, and the 5-year survival rate is between one and two percent. In contrast, the survival rates for earlier stages of the disease which may be detected by screening are much higher.


Centers for Disease Control and Prevention. What are the Risk Factors for Lung Cancer? Updated 05/06/14.

Straif, K. The IARC Monographs, Vol 100: A Review and Update on Occupational Carcinogens. International Agency for Research on Cancer. 23 Oct 2010.

Takiguchi, Y. et al. Chronic obstructive pulmonary disease as a risk factor for lung cancer. World Journal of Oncology. 2014. 5(4):660-6.

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