Lung Cancer Causes

Several causes of lung cancer are possible, but one thing is clear: Smoking is by far the greatest risk factor. While other causes exist, they pale in comparison to the risk caused by cigarette smoke.

Smoking and Nicotine

Tobacco smoke accounts for approximately 80 percent of lung cancer deaths in men, and 75 percent in women. The more cigarettes smoked per day, coupled with the number of years a person has smoked, increases the risk of lung cancer dramatically. Even if a person stops smoking, it takes ten to fifteen years before their risk of developing lung cancer drops close to the levels of non-smokers.

Cigarette smoke contains over 3,500 separate chemical compounds. Over forty of these chemicals are known carcinogens. Examples of these toxins include:

  • Cadmium
  • Nickel
  • Nicotine
  • Nicotine by-products
  • PAHs (polycyclic aromatic hydrocarbons)
  • Radioactive polonium 210
  • TSNAs (tobacco-specific nitrosamines).

Cigar smoke and pipe tobacco are not as high-risk as cigarette smoke, but are still contributing causes of lung cancer. People who smoke low-nicotine and filtered cigarettes are not at as high a risk as other smokers. Compared to non-smokers, however, they still have a much higher likelihood of lung disease and lung cancer.

ADT: Hope for Smokers?

Clinical trials are examining the cancer-fighting ability of a medication once prescribed to treat dry mouth. Initial studies suggest that anethole dithiolethione (ADT) may help prevent cancer in some former smokers. The medication may act like an antioxidant and attack abnormal respiratory cells.

Secondhand Smoke

Secondhand smoke is to blame for almost a third of all lung cancer cases, and 3,000 deaths a year are attributed to secondhand smoke. Secondhand smoke particles are smaller than regular tobacco smoke. As a result they are breathed in more easily and accumulate in the lungs. Over one hundred chemicals have been identified in secondhand smoke, many of them toxic.

Radon Gas

After tobacco smoke, radon gas is the second leading cause of lung cancer. Radon gas rises up out of the ground and can damage respiratory passages. The gas can enter buildings through wall cracks, pipes and foundations. Radon is colorless and odorless. The only way to detect the gas is to test for it. Radon gas test kits are inexpensive, and available through most hardware stores.

One out of every fifteen American homes may contain excessive amounts of radon gas.

Asbestos, Arsenic and Industrial Causes of Lung Cancer

Certain industries increase your likelihood of carcinogen exposure. Miners, for instance, are more likely to be exposed to radon gas. A number of industries work with uranium, another known carcinogen. Arsenic exposure can also increase the risks of lung cancer. In many areas, arsenic levels may be high in drinking water.

Asbestos is a mineral compound that breaks into small airborne shards. Breathing in asbestos can damage the respiratory tract. People who work with asbestos are three to four times more at risk for lung cancer. If the individual also smokes, the combination of asbestos and tobacco smoke increases risk levels to eight times that of other smokers.

Respiratory Disease

Certain respiratory diseases, such as tuberculosis, can damage and scar the lungs, which may increase the chance of cancer growth.

Prevention Techniques

The best way to avoid lung cancer is to…

  • Stop smoking.
  • If you don’t smoke, don’t start.
  • Avoid secondhand cigarette fumes.
  • Test your home for radon gas.
  • If you work with a known carcinogen, limit your exposure whenever possible.

Smoking Facts

  • Pipe and cigar smoke is almost as dangerous as cigarette smoke.
  • Over three million American teens smoke.
  • Cigarette smoke contains over forty known carcinogens.
  • 25.7 percent of adult American men smoke.
  • 21 percent of adult American women smoke.


Duke Comprehensive Cancer Center. (nd). Lung cancer facts.

National Cancer Institute. (updated 2002). What you need to know about lung cancer: Lung cancer: Who’s at risk? [NIH Publication No. 99-1553].

National Center for Health Statistics. (reviewed 2002). Smoking.

University of California at Berkeley Arsenic Research Program. (updated 2000). Arsenic lung accumulation study.