Smoking damages your body in minutes, not years as previously believed.
A recent study has shown that cancer-causing substances form very rapidly after smoking a first cigarette. Scientists observed the effects of polycyclic aromatic hydrocarbons (PAHs) on 12 subjects. PAHs are chemicals that are known to cause cancer. Within 15 to 30 minutes of inhalation, the PAHs were transformed by the body into another substances that causes cancer by damaging a person's DNA! This shows that the destructive process triggered by cigarettes actually begins with the FIRST one smoked! This is all the more reason for smokers to quit as soon as possible, and for non-smokers NEVER to begin in the first place.
(Source)