Smoking is a huge risk for lung cancer and chronic obstructive pulmonary disease, accounting for more than 75 percent of all deaths from these disorders. Smoking doubles the risk for cardiovascular disease deaths, but, because this disease is more prevalent, it accounts for as many smoking deaths as cancer and lung disease. The third major cause of tobacco-related mortality is chronic obstructive lung disease. Other common smoking-related diseases include low-birth-weight offspring, perinatal complications, other cancers (e.g., throat, bladder, and pancreas), and ulcers. Second-hand smoke increases the risk of cancer and heart disease in spouses and the incidence of respiratory and ear problems in children.
The tar in cigarette smoke is responsible for the cancers. Irritants and ciliotoxins appear to be responsible for lung diseases. Carbon monoxide and clotting factors appear to be the most likely causes of cardiovascular disease. The role of nicotine in cardiovascular disease appears to be much smaller than previously thought, and how many perinatal problems (including sudden infant death syndrome) are caused by carbon monoxide or by nicotine is debatable. Smokeless tobacco, pipes, and cigars cause oral cancers, especially when accompanied by heavy alcohol use.
Cessation of smoking almost eliminates the risk of heart disease in 5 years and of lung cancer in 20 years; however, the benefits of cessation are highly dependent on duration of smoking.

Measure the magnitude--Taking 10 puffs per cigarette × 20 cigarettes per day × 365 days per year × 20 years results in millions of drug self-administrations.

Cessation of smoking almost eliminates the risk of heart disease in 5 years and of lung cancer in 20 years; however, the benefits of cessation are highly dependent on duration of smoking.

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