Lung Cancer Causes

The Causes of Lung Cancer

Smoking and exposure to certain chemicals can greatly increase your risk of getting lung cancer.

Lung cancer is caused by a mutation in your DNA. When cells reproduce, they divide and replicate, forming identical cells, so that your body is constantly renewing itself. Inhaling harmful, cancer-causing substances (carcinogens) like cigarette smoke, asbestos, and radon, damages the cells that line your lungs. At first your body may be able to repair itself. With repeated exposure your cells become increasingly damaged. Over time, the cells begin to act abnormally and grow uncontrollably. This is how cancer can develop.

Several precancerous changes have to occur before cancer actually manifests. The buildup of extra cells causes tumors, which are either benign or malignant. Malignant cancerous lung tumors can be life threatening. They can spread and even return after they have been removed. According to the Centers for Disease Control and Prevention (CDC), nearly 90 percent of all lung cancers are due to smoking.

Personal History and Lifestyle Choices


Current research suggests that if a member of your immediate family (mother, father, sibling, aunt, uncle, or grandparent) has had lung cancer, you may have a slightly higher risk of developing the disease. This is true even if you don’t smoke. It’s unclear whether genetics causes lung cancer or merely increase your susceptibility to it. 


According to the American Cancer Society (ACS), lung cancer mostly occurs in older adults.  Two out of three people diagnosed with lung cancer are 65 or older. The average age at the time of diagnosis is about 70. The older you are, the longer you have been exposed to harmful chemicals. This naturally increases your risk for cancer.

Past Lung Disease

Past lung diseases, such as tuberculosis, and chronic obstructive pulmonary disease (COPD) — chronic bronchitis and emphysema — can cause inflammation and scarring in the lungs. You may be at a greater risk of developing lung cancer if you have a history of chronic diseases that affect the lungs.

Radiation Therapy to the Chest

Radiation therapy used to treat other cancers like non-Hodgkin’s lymphoma and breast cancer may increase your risk of lung cancer. This risk is higher if you smoke.

Secondhand Smoke

Even if you don’t smoke, being exposed to secondhand smoke at home, work, or in restaurants and bars can increase your risk of lung cancer. According to the CDC, each year about 3,000 people in the United States who have never smoked die from lung cancer due to secondhand smoke.


Smoking tobacco is the number one risk factor for lung cancer, accounting for nearly 90 percent of all cases. Tobacco and tobacco smoke contain more than 7,000 chemicals (like nitrogen oxide and carbon monoxide), many of which are carcinogenic. Inhaling the chemicals in a cigarette immediately triggers a change in lung tissue. Your body is initially able to repair the damage, but its ability to do so decreases as exposure continues. The more frequent and the longer you smoke, the greater your chance for lung cancer.


A balanced diet provides your body with the vitamins and minerals it needs to maintain good health. If you don’t eat a diverse mix of healthy foods, like fruits and vegetables, you may have an increased risk for lung cancer. This is especially true if you are a smoker.  

Environmental Factors


Radon is an odorless, colorless, and tasteless gas that occurs naturally with the breakdown of uranium in rocks and soil. These gases can seep into building foundations and into living and working spaces. Radon is difficult to detect and you could be exposed without knowing it. People who smoke have an increased risk from the affects of radon than those who don’t smoke. According to the CDC, radon is the second-leading cause of lung cancer in the United States.


Asbestos is an industrial material used in construction for insulation and as a fire retardant. When the material is disturbed, small fibers become airborne and can be inhaled. You are at a greater risk for developing lung cancer if you are exposed to asbestos on a regular basis.

Other Chemicals

Other chemical exposures can raise your lung cancer risks. Some examples are:

  • arsenic
  • beryllium
  • cadmium
  • vinyl chloride
  • nickel compounds
  • chromium compounds
  • coal products
  • mustard gas
  • chloromethyl ethers
  • diesel exhaust

 Learn which factors increase the risk of lung cancer.

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