About 90 % of all lung cancers are caused by tobacco use (Jemal, 2005). Lung cancer risk increases depending on the number of cigarettes that one has smoked and the duration of time when one has been smoking. Doctors tend to define this risk in the form of pack-years of an individual’s smoking history. They do this by multiplying the number of packets of cigarettes that one smokes per day by the number of years when one has been smoking.
Smoking pipe and cigar can also cause lung cancer, although in this case, the risk is not as high as in cigarette smoking. Tobacco smoke is known to contain about 4,000 chemical compounds, some of which have been proven to be carcinogenic or cancer-causing. The two primary carcinogenic chemicals found in tobacco smoke are polycyclic aromatic hydrocarbons and nitrosamines. When one ceases smoking, the risk of suffering from lung cancer decreases dramatically every year because damaged cells tend to be replaced by the continually-growing normal lung cells. For former smoker, it takes 15 years for the risk of developing lung cancer to become similar to that of a person who has never smoked.
Passive smoking can also cause lung cancer. Non-smokers can become passive smoking by inhaling tobacco smoke produced by smokers. This happens when these non-smokers share working or living quarters with smokers and has become an established risk factor for this type of cancer. According to The American Cancer Society, about 3,000 lung cancer deaths that are reported in the U.S every year are attributed to passive smoking.
Lung cancer can also be caused by radon gas, asbestos fibers, familial predisposition, lung diseases and air pollution. When one is exposed to asbestos, asbestos fibers can persist in the lung tissue for a lifetime, especially among individuals’ who work in settings where they are exposed to asbestos. Today, use of asbestos for acoustic and thermal insulation is banned or used in limited cases in many countries as a result of the danger of lung cancer that bring to people who work in the asbestos industry. Likewise, exposure to radon gas can increase the risk of getting lung cancer.
As for familial predisposition, numerous studies have indicated that lung cancer is likely to occur more among both non-smoking and smoking relatives of people who have suffered from lung cancer compared to the general population. Lung cancer survivors have a higher risk of suffering from the disease for the second time compared to other people. Finally, air population also raises the likelihood of someone suffering from lung cancer according to an observation made by Pope (2002). Experts believe that the lung cancer risk posed by breathing polluted air is similar to the risk caused by passive smoking.