Smoking causes lung cancer
The incidence of is strongly correlated with cigarette, with about 90% of cancers arising as a result of use. The risk of increases with the number of cigarettes smoked over time; doctors refer to this risk in terms of pack-years of history (the number of packs of cigarettes smoked per day multiplied by the number of years smoked). For example, a person who has smoked two packs of cigarettes per day for 10 years has a 20 pack-year smoking history. While the risk of lung cancer is increased with even a 10 pack-year smoking history, those with 30 pack-year histories or more are considered to have the greatest risk for the development of lung cancer. Among those who smoke two or more packs of cigarettes per day, one in seven will die of lung . But even though the risk is higher the more you smoke, there is no safe level of exposure to tobacco smoke.
Pipe and can also, although the risk is not as high as with cigarettes. While someone who smokes one pack of cigarettes per day has a risk for the development of lung that is 25 times higher than a nonsmoker, pipe and cigar smokers have a risk of lung that is about five times that of a nonsmoker.
Tobacco smoke contains over 4, 000 chemical compounds, many of which have been shown to be -causing, or carcinogenic. The two primary carcinogens in tobacco smoke are chemicals known as nitrosamines and polycyclic aromatic hydrocarbons. The risk of developing lung cancer decreases each year following as normal cells grow and replace damaged cells in the lung. In former smokers, the risk of developing lung cancer begins to approach that of a nonsmoker about 15 years after cessation of smoking.
Passive smoking, or the inhalation of tobacco smoke from other smokers sharing living or working quarters, is also an established risk factor for the development of lung cancer. Research has shown that nonsmokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with other nonsmokers. An estimated 3, 000 lung cancer deaths occur each year in the U.S. that are attributable to passive smoking.