Lung Cancer Facts

January 24, 2025

This page was reviewed under our medical and editorial policy by Jyoti Malhotra, M.D., M.P.H., associate professor, Department of Medical Oncology & Therapeutics Research, City of Hope^® Orange County Lennar Foundation Cancer Center; and Jae Y. Kim, M.D., associate professor, Division of Thoracic Surgery, Department of Surgery, City of Hope Cancer Center Duarte

Lung cancer is the leading cause of cancer deaths. The American Cancer Society (ACS) estimates 226,650 new cases of lung cancer will be diagnosed in 2025, and the disease will claim 124,730 lives. In the United States, 1 in 5 cancer deaths is due to lung cancer. However, new cases of lung cancer and deaths attributed to it have been lower each year because fewer people are smoking.

The five-year survival rate for lung cancer has improved by more than 20% in recent years to 26.6% across patients at any lung cancer stage, according to the American Lung Association.

Advances in treatment and detection are making it possible for patients to live longer.

What Is Lung Cancer?

Lung cancer begins when cells lining the air passages of the lung mutate and begin to grow uncontrollably. A pair of spongy organs in the chest, the lungs are separated into sections known as lobes. The right lung has three lobes and the left has two. (The left lung is smaller to make space for the heart.) When a person breathes in air through the mouth or nose, it travels down a tube known as the trachea. The trachea branches into a tree-like network of smaller tubes in the lungs called the bronchi and bronchioles. The air inflates tiny air sacs, called alveoli, which exchange oxygen for carbon dioxide in the blood.

Lung cancer develops when abnormal cells in the lungs grow and divide at a rapid pace — so fast that the cells in the immune system that fight disease are unable to keep up. These clusters of abnormal cells are called tumors. They may damage lung tissue and block the airways, causing issues like cough, chest pain or bleeding.

What Causes Lung Cancer?

Smoking is the leading cause of lung cancer, but people who have never smoked may still develop it. While roughly 80% of lung cancer deaths are due to a person smoking, exposure to secondhand smoke also contributes. That is because tobacco smoke contains thousands of chemicals, many of which are toxic. About 70 chemicals in tobacco smoke are known to cause cancer in animals or people. It’s important to note, however, that the incidence of lung cancer in nonsmokers has been rising, particularly among women of Asian descent.

Does Smoking Weed Cause Lung Cancer?

While it is not yet clear whether smoking marijuana causes lung cancer, marijuana smoke contains many of the same irritants, toxins and cancer-causing substances found in tobacco smoke. It is also known to depress immune system function. Smoking weed is not recommended due to the negative effects it has on the lungs. Patients considering it for medical use should discuss risks and benefits with their doctor, and consider alternatives to smoking it.

Does Vaping Cause Lung Cancer?

Because most electronic cigarettes (e-cigarettes) contain nicotine, they are considered tobacco products by the U.S. Food and Drug Administration (FDA). Whether vaping with e-cigarettes directly causes lung cancer is still unknown because they have not been on the market for a long time. But one chemical found in e-cigarettes, acrolein, may cause asthma and lung cancer. E-cigarettes also contain other chemicals that are known to cause lung and heart disease. Vaping may cause irreversible lung damage.

What Causes Lung Cancer in Nonsmokers?

After smoking, the second most common cause of lung cancer in the United States is exposure to radon. Radon is a naturally occurring, odorless gas from rocks and soil that may seep into homes through cracks or holes. Breathing in high levels of this radioactive gas over time may cause lung cancer cells to develop.

Other factors that may cause lung cancer in nonsmokers include:

• Exposure to secondhand smoke
• Having a close family member with lung cancer
• Working with asbestos, beryllium, nickel, arsenic, diesel exhaust, silica and chromium
• Exposure to air pollution
• Past radiation to the chest
• Exposure to radon and arsenic in well water

Lung Cancer Risk Factors

Risk factors are things that are known to increase the risk of a disease, but not all people with one or more known risk factors will get the disease.

For lung cancer, risk factors include the following.

Tobacco smoke: This includes smoking cigarettes, cigars and pipes. Exposure to other people’s smoke (known as secondhand smoke) also may increase the risk of cancer. Low-tar or “light” cigarettes and menthols pose almost the same risk as regular cigarettes.

Radon gas: Radon is a gas that is formed from the breakdown of uranium in rocks and soil. It has no taste or odor, and it may seep into homes where it becomes concentrated.

Asbestos: Asbestos is made of tiny fibers. Although its use is tightly regulated, it may be found in older homes and may become airborne as a result of renovations or demolition or deterioration, posing a serious health risk. People who routinely work with this material have an increased risk of lung cancer. Asbestos may also cause a type of cancer known as malignant mesothelioma, which affects the lining that surrounds the lungs.

Other carcinogens (cancer-causing substances): People who routinely work with certain chemicals, such as arsenic, beryllium, cadmium, chromium, coal, chloromethyl ether, mustard gas, nickel, silica, uranium and vinyl chloride may inhale them, increasing their risk of lung cancer.

Beta carotene supplements: Studies have linked the dietary supplement beta carotene to an increased risk for lung cancer.

Drinking water with high levels of arsenic: Unsafe levels of arsenic may be found in well water, but most people in the United States who get their water from a public water supply system are not at risk for high arsenic levels. Studies conducted in places such as South America and Southeast Asia have found a higher risk of lung cancer in people with high arsenic levels in their water.

Air pollution: Exposure to air pollution, including diesel exhaust, may increase the risk for lung cancer. An estimated 1% to 2% of lung cancer deaths in the United States may be due to outdoor air pollution, according to ACS.

Family history: Having a close family member with lung cancer may increase a person’s risk of developing it. This may be due to shared environmental factors, such as radon or tobacco smoke, or to genetics.

Age: People who are 65 years of age or older are at increased risk for lung cancer.

Other lung diseases: Having chronic obstructive pulmonary disease (COPD) or emphysema may increase a person’s risk of developing lung cancer, even if they have never smoked.

Is Lung Cancer Hereditary?

Having a parent or sibling with lung cancer may increase a person’s risk of developing it. Gene changes that a person gets from their parents are known as inherited genes or germline mutations. These changes in DNA, the molecule that carries genetic instructions in cells to help it function normally, may increase a person’s risk for certain cancers. 

Examples of germline mutations involved in lung cancer include changes in these genes: APC, ATM, BRCA1, CHEK2, EGFR, PALB2 and TP53.