Important Causes of Lung Cancer
by Beth G. Hodges, MD

The are several causes of lung cancer, but the foremost among them is smoking. 90% of lung cancers are directly related to smoking. The greater the exposure to tobacco smoke, the greater the risk. Significant risk is considered 30 pack years or more. Pack years are calculated and the number of packs smoked per day x the number of years. For example, a man who smoked 1 pack per day for 30 years and a woman who smoked 2 packs per day for 15 years both have a 30 pack year history.

Tobacco smoke contains around 4000 chemical that are considered carcinogens, or cancer -causing. Cigarette smoke contains the highest proportion of these chemicals, but pipe and cigar smoke also contain them to a slightly lesser degree. Low tar cigarettes have the same propensity to cause cancer as regular cigarettes. Read more about smoking and lung cancer here.

Secondhand smoke is also one of the important causes of lung cancer. It accounts for a high percentage of lung cancer cases, and increases the exposed person's risk by 24%. The more intense the exposure, the higher the risk. For example, someone who has worked their whole career in a bar, where smoking tends to be heavy, will have a higher risk than someone who worked beside a smoker whose smoke breaks were taken outside the office.

Asbestos is a silicate fiber that can deposit in the lungs of people who work around it (ie shipyard workers) and can increase the chances of developing lung cancer, especially mesothelioma, a cancer that grows from the pleura, or lining of the lung. Of interest is the fact that lung cancer in an asbestos worker rarely occurs if that person is not a smoker or exposed heavily to second-hand smoke. Asbestos workers who do not smoke have only a 5-fold increased risk of developing lung cancer, while those who do smoke have anywhere from a 50-90-fold increase in risk.

Radon gas is a naturally decaying product of uranium, and some houses in the United states and elsewhere can have high radon levels, which has been shown to increase the rate of lung cancer by 12%. One in fifteen homes in the United States has increased levels of radon. Test kits can be purchased for home testing of radon levels.

A family history of lung cancer, especially if found in more than one family member, can indicate a genetic weakness on chromosome 6 for the development of lung cancer. It is especially critical that teens with this history not pick up the tobacco habit.

Air pollution and occupations with exposure to arsenic or chromium or nickel also increase the risk of lung cancer slightly. Last but not least, someone who has survived one bout of lung cancer is statistically more likely to develop a second primary lung cancer than someone who has never had lung cancer.

The causes of lung cancer may be several, but it is important to remember that chief among them is smoking, smoking, smoking.

Published - September, 2009