Smoking addiction is harmful because it produces polycyclic aromatic hydrocarbons, which cause
cancer
Polycyclic aromatic hydrocarbons can result from the incomplete combustion of organic matter. These are carcinogenic and thus, cause cancer.
The carbon monoxide that is also produced by incomplete combustion of tobacco binds to haemoglobin and thus reduces oxygen transport. Nicotine stimulates the release of adrenaline and hence increases blood pressure. Nicotine is also responsible for the abnormal growth of the foetus in a pregnant woman.