A risk factor is something that increases your likelihood of getting a disease or condition.

It is possible to develop lung cancer with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing lung cancer. If you have a number of risk factors, ask your doctor what you can do to reduce your risk.

Some factors cannot be controlled, such as age, gender, or ethnicity. Almost all lung cancer is found in people over the age of 40 years, but it is most common in men after the age of 65 years. African-Americans, both men and women, carry a substantially higher risk of lung cancer than Caucasians.

It should be noted that although smokers carry the biggest burden of risk in developing lung cancer, it does occur in non-smokers. Like smokers, non-smokers are regularly exposed to airborne hazards that affect lung tissue and cause irritation and inflammation.

Risk factors for lung cancer include:


Nearly 85% of all lung cancers are associated with smoking. It is considered a direct and main cause, especially with small cell cancer. Smoke and carcinogens (cancer-causing agents) are inhaled into the lungs before they are absorbed into the bloodstream. Smokers regularly expose their lungs to carcinogens that irritate and damage cells that line the respiratory tract. This irritation and damage can alter the DNA of the cells, increasing the rate of cellular turnover. The risk of lung cancer increases with the number of years as a smoker and the number of cigarettes smoked. Smoking also includes other forms of tobacco found in pipes and cigars.

Long-term exposure to secondhand smoke also contributes to an increased risk of lung cancer.

Occupational or environmental exposures

Exposure to asbestos is associated with a specific type of lung cancer called mesothelioma. For people who work (or worked) with asbestos, the risk is even higher among those who smoke. Other lung irritants, such as wood smoke, burning coal, mine dust, metals, or paint also increase the risk of lung cancer. These exposures can occur in the workplace or at home.

Radon is a radioactive gas that occurs naturally in the soil. It is a colorless, odorless gas that seeps into buildings and homes. Long-term or heavy exposure to radon gas is associated with lung cancer risk. The risk is compounded in those who smoke.

Air pollutants, such as by-products from the combustion of diesel and other fossil fuels, are linked to lung cancer. Some people living outside of the US have an increased risk of lung cancer because of exposure to arsenic in drinking water.

Genetics and family history

Some genes are inherited, while others are acquired. Genetic make-up can influence risk by:

  • Making it more difficult to break down carcinogens in the body.
  • Making the lungs more vulnerable to the actions of carcinogens.
  • Having cells that do not have a mechanism to keep them from multiplying in a controlled manner (like brakes on a car).
  • Having cells that have a mechanism that accelerates cellular growth beyond the normal rate (like a gas pedal on a car).
  • Missing or have a specific gene that causes these changes.

People who have close family members, like parents, siblings, children, or other relatives, have a higher risk of lung cancer. The association is strongest in relatives who developed lung cancer at 60 years of age or younger.

Medical conditions or treatments

Medical conditions and/or treatments may increase the risk of lung cancer. This is because of inflammation, irritation, and scarring that cause lung damage. Some examples include:

  • Lung diseases, such as chronic obstructive pulmonary disease (COPD) and tuberculosis (TB).
  • HIV infection suppresses the body's immune system and causes lung diseases like pneumonia.
  • Radiation therapy—Previous treatment for lung or breast cancer for example, exposes the lungs to direct radiation.
  • Multiple endocrine neoplasia—associated with carcinoid tumors