What Causes Lung Cancer?

Lung cancer is the leading cause of cancer death worldwide. Smoking cigarettes and exposure to toxins can increase your risk of developing the condition.

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Lung cancer is the leading cause of cancer death worldwide and the third most common cancer in the United States. This condition occurs when cancerous cells begin to grow in the lungs. Lung cancer can either start in the alveoli (sacs in the lungs that help you breathe in air) or the bronchi (small tubes that carry oxygen to your lungs).

Smoking tobacco is the primary cause of developing lung cancer. If you currently smoke, you can substantially lower your lung cancer risk by quitting smoking. If you used to smoke, it is a good idea to regularly screen for this disease. Continuing smoking after receiving a lung cancer diagnosis may worsen your condition quickly.

However, smoking is not the only cause of lung cancer. Other factors that can increase your risk of developing the condition include being exposed to secondhand smoke or other toxins (like radon or asbestos) and having a family history of the disease.


Research suggests that 80–90% of all people who receive a lung cancer diagnosis are those who have a long history of smoking cigarettes and other tobacco products (e.g., pipes, cigars). People who smoke are up to 30 times more likely to get lung cancer than people who don’t use tobacco.

Cigarettes contain more than 7,000 toxic chemicals—and these toxins can damage the lining of the lungs, weaken the immune system, and prevent your body from fighting against cancer cells. Toxins from tobacco can also change the genetic structure of your DNA. If your DNA changes, lung cancer cells can grow out of control and create a tumor in your lungs.

Though the abnormal growth of cancer cells starts in the lungs, cancer cells can quickly metastasize (spread) to nearby tissue, lymph nodes, the blood, and other major organs. 

Secondhand Smoke

Unfortunately, exposure to secondhand smoke (smoke from someone else’s cigarettes) can also increase your risk of lung cancer. More than 7,000 lung cancer deaths each year are people who developed lung cancer due to secondhand smoke.

Inhaling secondhand smoke is not something you can always control. However, some ways to avoid exposure to secondhand smoke are to stay away from indoor public places that still allow smoking, move away from people in public who are smoking cigarettes, and ask people to not smoke in your home or car. 

Exposure to Toxins

In some cases, people with lung cancer developed the disease because of exposure to environmental toxins. Exposure to these chemicals may increase your risk of lung cancer:

  • Radon: The second leading cause of lung cancer, radon is a naturally occurring radioactive gas that is found in rocks and soil. Most radon exposure happens indoors in places like homes, schools, and workplaces. Radon is colorless and odorless, which makes it especially difficult to detect inside. However, a professional can test if you have radon at home and install a ventilation system to reduce radon levels. In some cases, you can also test your radon levels for free using at-home test kits that your local or state government office may provide.
  • Asbestos: Asbestos is a group of minerals that are made of heat-resistant materials. Before 1989, asbestos was used for a variety of things: building homes and cars, insulating hot water pipes, and making paint and plastics. In 1989, the U.S. Environmental Protection Agency (EPA) banned the use of asbestos due to its increased risk of health hazards, including lung cancer. Though the use of asbestos has significantly declined since the EPA ruling, asbestos may still be present in older buildings, pipes, and products.

Other types of elements that may also increase your risk of lung cancer are arsenic (found in soil, groundwater, and seafood), chromium (found in rocks, plants, and paints), and nickel (found in batteries and cars).

Is Lung Cancer Hereditary? 

Genetics can also play a role in your lung cancer risk. If a family member has had lung cancer, you may be more likely to develop the disease. 

There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Having a family history of lung cancer can increase your risk of SCLC. A study from the National Cancer Institute’s Center for Cancer Research found that you can inherit certain genetic changes (mutations) that can cause cancer cells to develop and grow out of control.

Who Gets Lung Cancer?

 Some people may be more likely to develop lung cancer than others. Certain demographic factors that can increase your risk of getting the condition include:

  • Age: Most people who receive a lung cancer diagnosis are over the age of 65.
  • Sex: Those who are assigned male at birth have a slightly higher risk of developing the condition than people assigned female at birth. But lung cancer is the second most common cancer in both males and females.
  • Ethnic background: Black men are more likely to get lung cancer than White men. Racial disparities in healthcare also reduce the likelihood of Black people receiving surgical treatment options for lung cancer, which increases their risk of dying from lung cancer.
  • Geographic location: Studies show that people living in rural areas may be more likely to develop lung cancer due to higher levels of tobacco use.

A Quick Review

Lung cancer is one of the most common cancers you can develop—and it’s also the most deadly. It can be scary to get tested for this condition. However, knowing the causes of the condition may help you reduce your risk of developing the disease. 

Smoking cigarettes is the leading cause of lung cancer. You can also get lung cancer via secondhand smoke, exposure to toxic chemicals like radon and asbestos, or having a family history of lung cancer. 

Quitting smoking and getting screened regularly for the disease (especially if you’re at an increased risk of lung cancer) can help prevent the onset of symptoms or get you an early diagnosis. Finding out about your lung cancer diagnosis in an early stage can help you get started on treatment sooner and improve disease progression down the road. 

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11 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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