The risk of developing lung cancer is 10 times greater for cigarette smokers than for nonsmokers. Decades of study in many countries have shown a direct link between smoking and lung cancer. Since cigar and pipe smokers do not inhale as much tobacco smoke, they have a slightly lower risk of lung cancer, but the risk is still significantly higher than it is for nonsmokers. Tar and nicotine, as well as smoke, play a role in the development of lung cancer. The risks for lung cancer increase proportionately with the number of cigarettes smoked, the length of time the person has smoked, the age at which the person started smoking, and the amount of smoke inhaled.
Other types of cancer caused by cigarette smoking include cancers of the throat, esophagus, bladder, kidney, pancreas, and mouth. Pipe and cigar smokers also have an increased risk for cancers of the lip and mouth. Since some of the tars in tobacco are swallowed, there is also an increased risk of stomach cancer. Respiratory diseases associated with smoking include chronic bronchitis, sinusitis, and emphysema. Each year in the United States, these diseases account for tens of thousands of deaths from respiratory failure. Cigarette smoking slows
down the action of the cilia, tiny hairlike projections that line the airways and help clean the lungs. When the cilia are immobilized, dust and dirt particles are able to invade the lungs and cause inflammation. As a result, cigarette smokers also have more chronic coughs, phlegm production, wheezing, and other respiratory symptoms. People with allergies and asthma are particularly vulnerable to the negative effects of cigarette smoke.