Any substance that is breathed in affects what happens to the lungs. Many of these substances can be hazardous and threaten the lungs' ability to work properly. Even one puff on a cigarette slows the cilia, weakening the lungs' ability to defend themselves against infections.
Cigarette smoke can cause air passages to close up and make breathing more difficult.
It causes chronic inflammation or swelling in the lungs, leading to chronic bronchitis. And cigarette smoke changes the enzyme balance of the lungs, leading to destruction of lung tissue that occurs in emphysema. Infections, lung irritants, cold weather, allergies, overexertion, excitement, inherited factors, even workplace chemicals and other irritants, play a part in this disease. Most people who develop TB today were infected years ago when the disease was widespread. Years or decades later, if the natural defense systems of people's bodies begin to weaken, the barriers they built up around the germs begin to crumble, and the TB germs escape and multiply.