Understanding Lung Cancer

Risk Factors for Lung Cancer

Last updated and reviewed on May 15, 2026. 

A risk factor is anything that increases your chances of getting a disease. When it comes to lung cancer, some risk factors are things we can control, like what we breathe into our lungs, while others are things we cannot change, like our age or the genes we get from our parents. Having one or even several risk factors does not guarantee you will get lung cancer, but it does mean your chances are higher than average.

It is important to remember that having one or more risk factors for a disease does not guarantee you will develop that disease. It is also possible to develop a disease even if you do not have any known risk factors. 

What raises your risk for developing lung cancer?

• Cigarette smoking is by far the most important risk factor for lung cancer. In the United States, smoking is linked to roughly 80 to 90% of all lung cancer deaths. Tobacco smoke contains more than 70 known cancer-causing chemicals, called carcinogens, that damage the DNA of lung cells every time smoke is inhaled. The risk goes up based on how many cigarettes a person smokes per day, how many years they have smoked, and how deeply they inhale. A person who smokes one pack of cigarettes a day for 20 years has a much higher risk than someone who smoked lightly for just a few years. Cigar and pipe smoking also raise the risk of lung cancer, though to a somewhat lesser degree than cigarette smoking. The encouraging news is that quitting smoking at any age lowers your risk, and the longer you stay smoke-free, the more your risk decreases over time.

• Secondhand smoke, also called passive smoking or environmental tobacco smoke, is the smoke that nonsmokers breathe in when they are around someone who is smoking. It is a serious risk factor in its own right. People who live with a smoker or work in environments where smoking is common are exposed to many of the same harmful chemicals as smokers themselves. Nonsmokers who are regularly exposed to secondhand smoke have about a 20 to 30% higher risk of developing lung cancer compared to people who are never exposed. Children who grow up in homes where adults smoke are also at risk, not just for lung cancer later in life, but for other respiratory problems in childhood.

• Radon gas is the second leading cause of lung cancer in the United States, responsible for about 21,000 deaths per year. Radon is a colorless, odorless, tasteless radioactive gas that forms naturally when uranium in soil and rock breaks down. It can seep up through the ground and into buildings through cracks in the foundation, gaps around pipes, or through building materials. Radon can build up to dangerous levels inside homes, schools, and workplaces, especially in basements and lower floors where ventilation is limited. Because you cannot see, smell, or taste it, the only way to know if your home has high radon levels is to test for it. Radon test kits are inexpensive and widely available at hardware stores. If high levels are found, there are effective ways to reduce radon in the home.

• Exposure to harmful substances at work is another significant risk factor for lung cancer. Some jobs put workers in regular contact with chemicals and materials that are known to cause lung cancer with long-term exposure. The most well-known of these is asbestos, a mineral that was widely used in construction, insulation, and shipbuilding before its dangers were understood. Workers who breathe in asbestos fibers over time can develop lung cancer, and the risk is much higher in those who also smoke. Other workplace substances linked to lung cancer include arsenic, chromium, nickel, beryllium, cadmium, diesel exhaust fumes, and coal or coke fumes. Workers in mining, construction, painting, rubber manufacturing, and certain chemical industries may face higher exposure. Wearing proper protective equipment and following workplace safety guidelines can help reduce but not always eliminate these risks.

• Air pollution from traffic, industry, and power plants contains fine particles and chemicals that, with long-term exposure, can raise the risk of lung cancer. The World Health Organization (WHO) has classified outdoor air pollution as a leading environmental cause of cancer deaths worldwide. People who live near busy roads, industrial areas, or in cities with high pollution levels face a higher risk over time. Indoor air pollution from burning wood, coal, or charcoal indoors, or from cooking with solid fuels in poorly ventilated spaces, is also a risk factor, particularly in parts of the world where this is common. While reducing exposure to air pollution can be challenging, steps like using air purifiers indoors, staying inside on high-pollution days, and advocating for cleaner community environments can make a difference.

• A personal history of lung cancer raises the risk of developing a second lung cancer. Even after successful treatment of the first cancer, the same underlying factors, whether they are genetic, environmental, or related to past smoking that led to the first cancer, may still be present in the remaining lung tissue. People who have already been treated for lung cancer are watched closely with regular follow-up scans and checkups for this reason. 

• Previous radiation therapy to the chest is also a risk factor. People who received radiation treatment for other cancers, such as Hodgkin lymphoma or breast cancer, especially at a young age, have a higher risk of developing lung cancer years later as a result of that treatment.

• Genetics and family history play a meaningful role in lung cancer risk. People who have a first-degree relative, a parent, sibling, or child who had lung cancer have a higher risk themselves, even if they have never smoked. This increased risk is thought to be due to both shared environmental exposures (like growing up in a home with a smoker) and inherited genetic factors. Scientists have identified specific inherited gene mutations that make a person's cells more vulnerable to the kind of DNA damage that leads to lung cancer. For example, changes in genes that control how the body processes tobacco smoke chemicals can make some people more susceptible to lung cancer even with lower levels of exposure. Genetic counseling and testing may be an option for people with a strong family history.

• Age is an important factor to understand. While lung cancer can occur at any age, it becomes significantly more common as people get older. Most people diagnosed with lung cancer are 65 or older, and the average age at diagnosis is around 70. This does not mean younger people are not at risk, especially if they smoke or have other risk factors, but age is a built-in part of why screening guidelines focus on older adults. As cells age, they accumulate more DNA damage over time, making it more likely that a mutation could eventually lead to cancer. Finally, some research suggests that sex may influence lung cancer risk. Women appear to be somewhat more susceptible to developing lung cancer from tobacco smoke than men, even when smoking habits are similar, and women who have never smoked are more likely to develop lung cancer than men who have never smoked. Researchers are still working to understand the hormonal and genetic reasons behind this difference.

Does Vaping raise your risk of lung cancer?

The science and studies are evolving regarding vaping and lung cancer. Here is what we know.

• Vaping alone (never-smokers). No significant increased risk of lung cancer was found in never-smoking current vapers in at least one systematic review ¹. However, one study found that non-smoker vapers had faster lung aging than never-smokers, suggesting an increased risk of age-related lung disease, including cancer ². The honest answer is that e-cigarettes simply haven't been around long enough to generate the decades of follow-up data needed to draw firm conclusions.

• Vaping + smoking (dual use). This is where the signal is clearest and most concerning. Adjusted odds ratios revealed a fourfold higher risk of lung cancer among individuals who vaped in combination with chronic smoking versus individuals who only smoked ³. A 2024 systematic review suggests a potential association between e-cigarette use and increased lung cancer risk, particularly among dual users, though causality cannot be established due to heterogeneity and limited longitudinal data ⁴.

• Former smokers who switch to vaping. Former cigarette smokers who use e-cigarettes or vaping devices may be at higher risk for lung cancer than those who don't vape, with those who had quit smoking for less than five years found to have both a higher risk of lung cancer and lung cancer mortality than non-e-cigarette users ⁵.

Why does the concern exist chemically?

E-cigarettes contain nicotine derivatives such as nitrosamines, heavy metals including organometal compounds, polycyclic aromatic hydrocarbons, and flavoring aldehydes, several of which are known or suspected carcinogens. ⁶.

Research so far shows that legal e-cigarettes are far less harmful than smoking and can help people stop smoking -- but they are not risk-free, and we don't yet know their long-term effects ⁷. 

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