Additional Risk Factors
In the United States, roughly 10% to 20% of lung cancers—about 20,000 to 40,000 cases each year—occur in people who have never smoked or who have smoked fewer than 100 cigarettes in their lifetime (1). Lung cancer can also be caused by risk factors other than cigarette smoking, including radon, asbestos, secondhand smoke, and other environmental exposures. Learn more about these risk factors below.
What is radon?
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The diagram above displays the step-by-step flow of uranium and radon into a household (6).
Radon
Radon is a natural, odorless, and tasteless gas created from uranium undergoing radioactive decay (2). Uranium can be found in soil and rocks, and radon gas can be released into the air or water. Radon can also decay into radiation. High energy alpha radiation can be created as a byproduct from decay and can localize into the lung tissue (3). Radon leads to poor health outcomes, such as cancer, arthritis, diabetes, and ulcers (2). It is the primary cause of lung cancer that is unrelated to smoking (6).
What are some statistics on radon(7)?
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In 2025, about 1,384 out of 14,099 lung cancer cases were reported as radon-induced lung cancer in New York
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In 2025, about 59 out of 278 lung cancer cases were reported as radon-induced lung cancer in Wyoming
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In 2025, about 966 out of 5,032 lung cancer cases were reported as radon-induced lung cancer in Indiana
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For more information about the radon-induced cases in your state, visit https://aarst.org/Report-Cards/IN-Report-Card.html
How do you know if you have been exposed?
Low levels of radon can be in outdoor air, whereas it can attach to dust and exposure occurs as dust gets inhaled. High levels of radon are contained indoors in homes, schools, or office buildings. Furthermore, cracks in the basement or in the foundation of a home can increase levels of radon inside (4). Since radon is created from uranium, be aware of areas with high levels of uranium, such as mining or milling operations that involve metals or phosphates. Radon can also be found in drinking water or airborne when that water gets used for cooking or showering. According to the Environmental Protective Agency (EPA), 1 out of 15 homes have high radon levels (2).
Radon in our Homes (5)
The science of radon in the our homes and how it is dangerous.
How can I test my home for radon?
Governmental Recommendations:
According to the EPA, if measured indoor levels of radon are 4 or greater picocuries per liter of air (4 pCi/L) (5). Levels below 4 can still be harmful, though. They recommend using a certified radon mitigation specialist to ensure appropriate methods are used to lower radon levels.
Radon toolkits:
You can obtain a radon test kit through your state radon office for resources in your area. You can either hire a radon tester or purchase a radon test kit from your local radon office, hardware store, or by calling 1-800-SOS-Radon. There are different tests, but they all come with lists of instructions and resources for more detailed information (3). Once you complete the steps, you send it to a lab and wait for the results. If the levels are above 4, then test it a second time to confirm. If it is 4 again, it is time to take action: contact your state radon office and find a specialist, a mitigation contractor, and they can reduce the levels. After the repairs are made, be sure to test your home again. Just because your neighbor’s home has low levels, this is not a good indicator of the radon levels in your personal home.
Related Resources (1,2)
Contacting a specialist: 1–800–557–2366
If you are in need of commercial testing: https://nrpp.info/pro-search/
Ordering radon testing kits and instructions:1–800–767–7236
More information regarding radon reduction in the household: 1-800-644-6999
What is asbestos?
Asbestos
Asbestos is a group of six naturally occurring fibrous silicate minerals known for their heat resistance, strength, and chemical durability. Commonly used in construction materials, insulation, and automotive parts, these microscopic fibers are dangerous when inhaled. Exposure to asbestos results in serious risks of developing mesothelioma and lung cancer (9).
The diagram above outlines common places in the home asbestos can be found (10).
What are some statistics on asbestos (11)?
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The National Cancer Institute confirmed that asbestos causes lung cancer in 1942.
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Asbestos exposure is the primary cause of about 4% of lung cancer cases.
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Smoking increases your risk of developing lung cancer from other harmful substances such as asbestos, arsenic and diesel exhaust.
How do you know if you have been exposed?
Most people encounter asbestos at some point in their lives, as small amounts of the mineral are present in the environment. The World Health Organization (WHO) reports that millions of individuals are exposed to asbestos worldwide, with the majority of exposures occurring in occupational settings (12). To learn more about whether you may have been exposed to asbestos, click here to explore common sources and locations where it is often found.
Secondhand smoke
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Secondhand smoke is the third most common cause of lung cancer in the United States.
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If you don’t smoke, breathing in the smoke of others can increase your risk of developing lung cancer (13).
What is secondhand smoke?
Secondhand smoke, also known as environmental tobacco smoke, is a combination of two types of smoke produced during tobacco use. Mainstream smoke is exhaled by the person actively smoking, while sidestream smoke comes directly from the burning end of tobacco products such as cigarettes, cigars, pipes, or hookahs (13).
Is secondhand smoke dangerous?
Inhaling secondhand smoke exposes individuals to nicotine and other toxic chemicals in much the same way as active smoking. Greater exposure leads to higher concentrations of these harmful substances in the body. Importantly, there is no safe level of secondhand smoke exposure (13).
Does secondhand smoke cause cancer?
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Secondhand smoke is a well-established cause of cancer. It contains more than 7,000 chemicals, around 70 of which are known carcinogens.
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Exposure to secondhand smoke can lead to lung cancer, even among people who have never smoked (13).
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Research also suggests it may increase the risk of several other cancers in adults, including cancers of the:
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larynx (voice box)
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nasopharynx (the area of the throat behind the nose)
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nasal sinuses
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breast.
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Where is secondhand smoke?
At work
Workplaces are a common source of secondhand smoke exposure for adults. Although many laws have made offices and public spaces smoke-free, smoking is still permitted in some settings. The Surgeon General has identified smoke-free workplace policies as the most effective way to protect employees, while also encouraging smokers to reduce or quit (13).
At home
Maintaining a smoke-free home is one of the most important steps to protect your family. Secondhand smoke can harm anyone, but children are especially vulnerable to its toxic effects. In multi-unit housing, smoke can spread through ventilation systems, walls, and shared areas, exposing nearby residents even if they do not live in the same unit (13).
Public spaces
Exposure can still occur in public settings where smoking is allowed, such as certain restaurants or outdoor areas. Supporting smoke-free environments and choosing smoke-free establishments can help reduce risk. Areas designed for children, including schools and daycare centers, should always remain smoke-free (13).
In the car
Smoking inside a vehicle can rapidly lead to a buildup of harmful chemicals, even when windows are open. This poses a particular risk to children. Many health organizations recommend keeping cars smoke-free, and some regions have laws that prohibit smoking in vehicles when young passengers are present (13).
Workplace exposure to carcinogens
In some occupations, workers may come into contact with substances that increase the risk of developing lung cancer. These exposures can include radioactive materials such as uranium, toxic elements like arsenic, and industrial compounds containing silica or chromium. In addition, inhalation of pollutants such as diesel exhaust is another recognized occupational hazard linked to elevated cancer risk (13).
Arsenic in drinking water
Studies from regions in Southeast Asia and South America have found that consuming water with high arsenic levels is associated with a greater risk of lung cancer. However, these concentrations are far above what is typically present in the United States. For most Americans, particularly those served by public water systems, drinking water is not a significant source of arsenic exposure (13).
Personal or family history of lung cancer
People who have had lung cancer before are more likely to develop it again. Close relatives, like siblings or children, may also face a somewhat higher risk, especially when the cancer occurred at a younger age. This is thought to result from a combination of genetic factors and shared environmental exposures, including tobacco smoke. In some cases, inherited traits appear to play a role (13).
Air pollution
Exposure to air pollution in urban areas, including pollutants from diesel exhaust, can modestly raise the risk of lung cancer. However, this risk is far smaller than the risk associated with smoking. In the United States, outdoor air pollution is thought to contribute to roughly 1–2% of lung cancer deaths (13).
References:
1. Centers for Disease Control and Prevention. (2025, February 13). Lung cancer risk factors. U.S. Department of Health and Human Services. https://www.cdc.gov/lung-cancer/risk-factors/index.html
2. CDC. Radon Resources. Radon. Published December 26, 2024. Accessed June 1, 2025. https://www.cdc.gov/radon/communication-resources/index.html
3. Radon and Cancer. Cancer.gov. Published December 6, 2011. Accessed June 1, 2025. https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/radon/radon-fact-sheet#where-can-people-find-more-information-about-radon
4. Radon | Department of Public Health & Environment. cdphe.colorado.gov. https://cdphe.colorado.gov/hm/radon
5. Radon Report Card | Indoor Environments Association. Aarst.org. Published 2025. Accessed June 1, 2025. https://aarst.org/report-card/
6. Radon in our Homes: The Science Behind the Danger | Aaron Goodarzi | TEDxYYC. www.youtube.com. https://www.youtube.com/watch?v=tHoITOI1d8k
7. How Does Radon Get Inside Your Home? | Certified Environmental Contractors. Certified Environmental Contractors. Published May 7, 2024. Accessed June 18, 2025. https://www.certified-enviro.com/blog/how-does-radon-get-inside-your-home/
8. Radon Report Card | Indoor Environments Association. Aarst.org. Published 2025. https://aarst.org/report-card/
9. Uguen, M., Dewitte, J.-D., Marcorelles, P., Loddé, B., Pougnet, R., Saliou, P., De Braekeleer, M., & Uguen, A. (2017). Asbestos-related lung cancers: A retrospective clinical and pathological study. Molecular and Clinical Oncology, 7(1), 135–139. https://doi.org/10.3892/mco.2017.1277
10. Poughkeepsie Environmental & Construction Group. (n.d.). Learn how to locate asbestos in your home. https://www.poughkeepsieenv.com/articles/learn-how-to-locate-asbestos-in-your-home
11. Selby, K. (2022, July ?). 49 key lung cancer statistics you should know | Asbestos exposure. Asbestos.com. https://www.asbestos.com/cancer/lung-cancer/statistics/
12. Cleveland Clinic. (2024, January 10). Asbestosis. https://my.clevelandclinic.org/health/diseases/22245-asbestosis
13. American Cancer Society. (2024, January 29). Lung cancer risk factors. American Cancer Society. https://www.cancer.org/cancer/types/lung-cancer/causes-risks-prevention/risk-factors.html