Smoking injures lung tissue. Tissue damage from smoking can lead to chronic obstructive pulmonary disease (COPD), which is sometimes called emphysema.
With COPD, the airways and air sacs lose their elasticity and the walls between many of the air sacs are destroyed. The walls of the airways also become inflamed and swollen and more mucous is formed. As a result it becomes very difficult to get air in and out of the lungs. Because these changes happen slowly over a number of years, a person may not notice the changes until it’s too late.