Tobacco smoke contains over 4000 chemicals, at least 43 of which are known to cause cancer of the mouth, pharynx, larynx, oesophagus, lung, pancreas, stomach, kidney, cervix, vulva, penis, bladder and anus. Nicotine is the addictive drug in tobacco. The mixture of nicotine and carbon monoxide in each cigarette you smoke temporarily increases your heart rate and blood pressure, straining your heart and blood vessels. This can cause heart attacks and stroke. It also slows your blood flow, cutting off oxygen to your feet and hands.
Some smokers end up having their limbs amputated.
Tar coats your lungs like soot in a chimney and causes cancer. A person who smokes 20 cigarettes a day breathes in up to 150ml of tar in a year. Over time, your airways narrow and let less air into your lungs. The strain put on your body by smoking often causes years of suffering. People with emphysema often get bronchitis again and again, and suffer lung and heart failure.