What Causes Lung Cancer?

Medically Reviewed by Melinda Ratini, MS, DO on April 27, 2023
4 min read

Lung cancer is one of the most common types of cancer worldwide. It happens when the cells in your lungs mutate, or change. The most common cause of these changes is when you breathe in toxic substances. Lung cancer can develop many years after you have inhaled the damaging fumes.

A variety of things cause lung cancer.

Cigarette smoke.Smoking causes about 90% of lung cancer cases. It also has a link to more than a dozen other types of cancer. Cigarettes have about 250 harmful chemicals, and 69 of them cause cancer. It doesn’t matter how much you smoke. Even one cigarette a day puts you at risk for lung cancer.

It’s not only a risk for the smoker. Secondhand smoke, or smoke you inhale from a lit cigarette or from a smoker, is also known to cause this disease. People who don’t smoke have a 20%-30% higher risk for lung cancer if they’re around secondhand smoke at work or home.

Your risk for lung cancer goes down when you quit. Even if you get cancer, your chance of dying from it drops by 30%-40% if you stop smoking. It helps your body heal faster and lessens your chance of the cancer coming back.

Vapes. These are also called electronic cigarettes, or e-cigarettes. The liquids in a vape contain nicotine, flavoring chemicals, and other toxic substances you breathe in. They’re poisonous to the cells in your lungs.

We’re not sure yet if vaping causes lung cancer. The vapor from e-cigarettes does contain chemicals that are known to cause cancer, but in lesser amounts than you find in cigarettes. If you vape, you may become addicted to nicotine or even start smoking cigarettes in the future.

Marijuana. It’s unclear if marijuana is a lung cancer risk. People who use it may also smoke cigarettes. This makes it hard to say if it alone causes lung cancer.

How you use marijuana makes a difference. Most people smoke it. You can also get it in food, drinks, pills, and other products. Marijuana smoke contains many of the same toxins as tobacco smoke. This raises your risk for conditions that affect your breathing, like bronchitis. And it may weaken your immune system. You inhale it more deeply than cigarettes. This can leave 4 times more tar on your lungs than cigarettes.

We need more research to find out if it causes lung cancer. Some studies suggest that the tetrahydrocannabinol (THC) and cannabidiol (CBD) in marijuana may work against tumors.

Radon. You can’t see, smell, or taste this gas. It’s found in soil and rocks and gives off radiation. Radon enters homes, schools, and other buildings through small cracks in the foundation. It seeps into 1 in 15 homes in the U.S. and causes about 21,000 lung cancer deaths each year. After cigarettes, it’s the second biggest risk factor for lung cancer.

It’s easy and important to test your home for radon. Your neighbor may have a positive result and you may not. The only way to find out if you do is with a test. The kits are affordable, and you can order one online or from your local health department.

Asbestos. This is a substance that’s known to cause cancer for people who are around it on a regular basis. Asbestos is made up of minerals found in soil and rocks. It’s used in buildings, homes, cars, and other products.

When you work with asbestos, it breaks down into tiny fibers that you inhale. These fibers get stuck in your lungs. If you’re around it for a long time, the asbestos builds up in your lungs. This makes it hard to breathe and can damage your health. A common cancer for people who work around asbestos is mesothelioma. It is a cancer of the chest and stomach. Asbestos is also linked to lung, larynx, and ovary cancers.

Particle pollution. This is a mix of tiny pieces of acids, chemicals, dust, and metals in the air. Each particle is much smaller than a grain of sand. They can get trapped in your lungs when you breathe them in. It’s known to cause lung cancer.

There are ways that you can lower your chances of lung cancer from particle pollution:

  • Pay attention to the air quality forecast each day.
  • Stay inside when pollution is high.
  • Don’t exercise next to busy highways at any time.

Genes. Families pass genes from one generation to the next. This includes mutated genes that make your cells unable to fix damaged DNA, and others that make your body unable to remove cancer-causing chemicals from your system.

Tell your doctor if someone in your family has had the disease. This raises your chances of having it. Around 8% of lung cancers are caused by a gene passed down through families.