Lung cancer, like all cancers, results from an abnormality in the body’s basic unit of life, which is the cell. The principal function of the lungs is to exchange gases between the air we breathe and the blood. Lung cancer is the most common cause of death due to cancer in both men and women throughout the world. It is predominantly a disease of the elderly; almost 70% of people diagnosed with lung cancer are over 65 years of age, while less than 3% of lung cancers occur in people under 45 years of age. The median age at diagnosis is 70 years. As today, August 1 is set aside for global awareness of the deadly disease, below are some major risk factors you should know: Smoking The incidence of lung cancer is strongly correlated with cigarette smoking, pipe and cigar smoking, with about 90% of lung cancers arising as a result of tobacco use. The risk of lung cancer increases with the number of cigarettes smoked and the time over which smoking has occurred Passive smoking Passive smoking or the inhalation of tobacco smoke by non-smokers who share living or working quarters with smokers, also is an established risk factor for the development of lung cancer. Research has shown that non-smokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with non-smokers who do not reside with a smoker. The risk appears to increase with the degree of exposure (number of years exposed and number of cigarettes smoked by the household partner) to second-hand smoke. It is estimated that over 7,000 lung cancer deaths occur each year in the U.S. that are attributable to passive smoking. Exposure to asbestos fibers Asbestos fibers are silicate fibers that can persist for a lifetime in lung tissue following exposure to asbestos. The workplace was a common source of exposure to asbestos fibers, as asbestos was widely used in the past as both thermal and acoustic insulation. Today, asbestos use is limited or banned in many countries, including the U.S. Both lung cancer and mesothelioma (cancer of the pleura of the lung as well as of the lining of the abdominal cavity called the peritoneum) are associated with exposure to asbestos. Exposure to radon gas Radon gas is a natural radioactive gas that is a natural decay product of uranium that emits a type of ionizing radiation. Radon gas is a known cause of lung cancer, with an estimated 12% of lung cancer deaths attributable to radon gas, or about 21,000 lung-cancer-related deaths annually in the U.S., making radon the second leading cause of lung cancer in the U.S. after smoking. Lung diseases The presence of certain diseases of the lung, notably chronic obstructive pulmonary disease (COPD), is associated with an increased risk (four- to six-fold the risk of a nonsmoker) for the development of lung cancer even after the effects of concomitant cigarette smoking are excluded. Pulmonary fibrosis (scarring of the lung) appears to increase the risk about seven-fold, and this risk does not appear to be related to smoking. Air pollution Air pollution from vehicles, industry, and power plants can raise the likelihood of developing lung cancer in exposed individuals. Up to 1%-2% of lung cancer deaths are attributable to breathing polluted air, and experts believe that prolonged exposure to highly polluted air can carry a risk for the development of lung cancer similar to that of passive smoking. Exposure to diesel exhaust Exhaust from diesel engines is made up of gases and soot (particulate matter). Many occupations, such as truck drivers, toll booth workers, forklift and other heavy machinery operators, railroad and dock workers, miners, garage workers and mechanics, and some farm workers are frequently exposed to diesel exhaust. Studies of workers exposed to diesel exhaust have shown a small but significant increase in the risk of developing lung cancer. Genetic susceptibility While majority of lung cancers are associated with tobacco smoking, the fact that not all smokers eventually develop lung cancer suggests that other factors, such as individual genetic susceptibility, may play a role in the causation of lung cancer. Numerous studies have shown that lung cancer is more likely to occur in both smoking and non-smoking relatives of those who have had lung cancer than in the general population. It is unclear how much of this risk is due to shared environmental factors (like a smoking household) and how much is related to genetic risk.