Tobacco smoking affects nearly every organ of the body, and causes or contributes to many different types of cancer. Because tobacco smoke contains over 4,000 chemicals, it is not surprising that it can cause major harm to the lungs. Lung damage caused by smoking can come from direct inhalation by a smoker, or from passive smoking caused by simply breathing in the vicinity of someone who is smoking.
General
Tobacco smoke contains tar, a substance that damages your lungs' airways. Your immune system responds by sending cells to protect your lungs, but tobacco smoke destroys them, too. Substances released by these dead cells further damage your lungs, according to the British Lung Foundation. Nicotine, the addictive substance in tobacco, makes only a small contribution to the lung damage caused by smoking.
Lung Cancer
Smoking causes 85 percent of all lung-cancer deaths in the United States, according to the American Lung Association. It is the leading cause of cancer deaths in women, and kills over 150,000 people a year in the United States alone. Although most cases of lung cancer occur in people older than 60, the five-year survival rate of only 15.6 percent is among the lowest of all cancers.
COPD
Chronic obstructive pulmonary disease, known as COPD, refers to one or both of two conditions--chronic bronchitis and emphysema. Cigarette smoking is the leading cause of COPD, according to the National Heart Lung and Blood Institute. People develop COPD when the airways and tiny air sacs of the lungs become damaged. Tobacco smoke causes air sacs to lose elasticity and destroys the walls separating them, leading to emphysema. The smoke also inflames the airways of the lungs, causing mucus to form, and reduces the amount of air flowing through them, leading to chronic bronchitis. These conditions can prevent you from performing any activity that requires physical exertion. Because the damage to the lungs is permanent, once you are diagnosed you will not recover completely, even if you quit smoking.
Passive Smoking
Passive smoking, also known as secondhand smoking, occurs when you breathe in smoke that has been expelled from the lungs of a smoker or from the end of a burning tobacco product. Passive smoking can damage your lungs in the same ways that direct smoking can, although the risks are generally not as dramatic. The American Lung Association estimates that passive smoking causes more than 3,000 lung cancer deaths in the United States every year. It can also trigger asthma attacks in children.
Effect of Quitting
Quitting smoking after many years will not repair all of the damage you have done to your lungs. Nevertheless, it will repair some of it. The extent to which your lungs rebound depends on how long you've been smoking. Quitting smoking can dramatically increase the functioning of your lungs in as little as one month, according to the American Cancer Society. If you manage to stay free of cigarettes for 10 years, you will have cut your risk of lung cancer to half of what it was when you first quit.
