Lung cancer risk factors

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Kim-Son H. Nguyen M.D. Cafer Zorkun, M.D., Ph.D. [2]

Overview

The most potent risk factor in the development of lung cancer is tobacco smoking. Other risk factors include secondhand smoke, air pollution, family history of lung cancer, radiation therapy to the chest, radon exposure, asbestos exposure and exposure to other chemical carcinogens.

Common risk factors

The following may increase one's risk of lung cancer:

• Smoking
• Second-hand smoke
• Family history of lung cancer
• High levels of air pollution
• Radiation therapy to the chest
• Radon gas
• Asbestos
• High levels of arsenic in drinking water
• Occupational exposure to chemical carcinogens
• Previous lung disease
• Indoor burning of coal
• Weakened immune system
• Lupus

Smoking

• Cigarette smoking is the leading cause of lung cancer.
• Both active and passive smoking are associated with increased risk of lung cancer.
• The risk of lung cancer is associated with increased quantity of cigarette smoking as well as increased duration of smoking.
• There is no evidence that smoking low-tar cigarettes lowers the risk (however lung cancer has occurred in people who have never smoked).
• The more cigarettes you smoke per day and the earlier you started smoking, the greater your risk of lung cancer.
• Recently introduced e-cigarrettes, which were thought to be risk-free were recently demonstrated to be also associated with a significantly increased risk of lung cancer due to the presence of formaldehyde.
• In the United States, smoking is estimated to account for 87% of lung cancer cases (90% in men and 85% in women).*There is approximately a 20 year lag period between smoking and death due to lung cancer (in men). Shown below is an image depicting the correlation between smoking and lung cancer.

The incidence of lung cancer is highly correlated with smoking. Source: NIH.

Second-hand smoke

• Second-hand smoke is what smokers exhale and what rises from a burning cigarette, pipe or cigar. It is also called environmental tobacco smoke (ETS), or involuntary or passive smoking.

• Second-hand smoke contains the same chemicals as smoke that is actively inhaled. People exposed to second-hand smoke have an increased risk of lung cancer. Second-hand smoke is a main risk factor for lung cancer among non-smokers. No amount of exposure to second-hand smoke is safe.

Air pollution

• Emissions from automobiles, factories and power plants are thought to pose potential risks.

• Researchers have shown that individual components of outdoor air pollution cause cancer. These components include diesel engine exhaust, benzene, particulate matter and some polycyclic aromatic hydrocarbons (PAHs).

Family history of lung cancer

• Family history of lung cancer may increase the risk of lung cancer.
• First-degree relatives of people who have had lung cancer may have a slightly higher risk of developing lung cancer themselves. The increased risk among first-degree relatives could be due to a number of factors, such as shared behaviors or living in the same place where there are carcinogens.
• Studies of families with a strong history of lung cancer have found that the increased risk might be due to a mutation in a lung cancer gene. Other studies have shown that the risk of lung cancer in a family increases if a family member developed the disease at an early age.

Radiation therapy to the chest

• A history of radiation therapy to the chest increases the risk of lung cancer due to the development of cellular damage and DNA mutations.
• The risk of lung cancer increases for people who have had previous exposure to ionizing radiation.
• People who have been treated with radiation therapy to the chest for cancers such as Hodgkin lymphoma or breast cancer are at increased risk for lung cancer. The risk is further increased in people who smoke.

Radon exposure

• Radon is a colorless, odorless, tasteless gas that comes from the natural breakdown of uranium in rocks and soil. In the outdoors, radon gas is diluted by fresh air, so it is not usually a concern. But radon can seep into a home or building through dirt floors or cracks in basement foundations. It may reach unsafe levels in enclosed, poorly ventilated homes or buildings because of seepage into the basement. Breathing in radon gas can damage cells that line the lungs.

• Radon exposure increases the risk of lung cancer. Radon is the leading cause of lung cancer in non-smokers and the second leading cause of lung cancer in smokers.

• The risk of developing lung cancer depends on how much radon a person is exposed to, how long they are exposed as well as whether or not they smoke. The risk from radon is much higher in people who smoke than in those who don't.

Asbestos exposure

• Asbestos is group of minerals that occur naturally. Asbestos has been widely used in building materials and many industries. Exposure to asbestos fibers in the air that people breathe increases the risk of lung cancer.
• The risk of asbestos exposure is highest for people who work with asbestos, such as miners or those who work with it in manufacturing.
• Studies have shown that the combination of smoking and asbestos exposure is especially hazardous. People who are exposed to asbestos and also smoke are at even greater risk of developing lung cancer.

Exposure to other chemical carcinogens

• Arsenic and inorganic arsenic compounds
• Beryllium and beryllium compounds
• Cadmium and cadmium compounds
• Chemicals used in rubber manufacturing, iron and steel founding and painting
• Chloromethyl ethers and bischloromethylether
• Chromium (VI) compounds
• Cobalt-tungsten carbide
• Diesel engine exhaust
• Mustard gas
• Polycyclic aromatic hydrocarbons (PAHs)
• Radioactive ores such as uranium and plutonium
• Silica dust and crystalline silica
• Some nickel compounds

Less common risk factors

• Smoking marijuana
• Indoor burning of wood
• High-temperature frying
• Meat-diet
• Physical inactivity
• Occupational exposure to certain chemicals
• There may be some association between lung cancer and occupational exposure to vinyl chloride, dioxin, cobalt-tungsten carbide, or strong inorganic acid mists, but more research is needed to be sure. Research to date does not provide a conclusive link between pesticides and cancer, but the evidence does suggest a possible association with lung cancer.
• Removal of both ovaries