Emphysema is caused by the chemicals in tobacco smoke. Lung tissue is destroyed and the lungs develop large holes that blow up like balloons. This makes breathing very difficult and is caused by heavy smoking. It is a disease of the alveoli. If the alveoli have been broken, blown up, or blocked by tar, the surface area is reduced. This makes oxygen exchange more difficult. Emphysema makes people breathe faster and wheeze.
Carcinogens are in tobacco smoke and cause cancer of the lungs, mouth, gullet and bladder. Nine out of ten people who die of lung cancer are heavy smokers.
Bronchitis is mostly a smoker's disease. The passages to the lungs are swollen and sore because the smoke irritates them. Tiny hairs called cilia usually keep these passages clear but these cilia are stopped working by cigarette smoke and the lungs fill with mucus and tar. People try to remove the mucus by coughing. This is smokers cough. Smokers get chronic bronchitis because the cilia aren't working. None smoker's get acute bronchitis. Bronchitis is caused by an infection which makes the body produce more mucus, so non-smokers' cilia can remove the mucus and the bronchitis goes.
Tobacco smoke can cause sore eyes, throat, and can cause headaches. It can irritate babies and make hay-fever and asthma worse.
Pregnant mothers who smoke have smaller babies, which means the child may be weaker.
Heart disease is three times more common amongst smokers. Smoking increases and encourages fat to be deposited on the artery walls and nicotine narrows them. This leads to chest pains and perhaps a heart attack.