Second hand smoke is a mixture of the smoke given off by the burning end of a cigarette, pipe, or cigar, and the smoke exhaled from the lungs of smokers. This mixture contains more than 4,000 substances, more than 40 of which are known to cause cancer in humans or animals and many of which are strong irritants.
Second hand smoke is also called environmental tobacco smoke (ETS); exposure to secondhand smoke is called involuntary smoking or passive smoking.
When a cigarette is smoked, about half of the smoke generated is ETS. As the exposure to second hand smoke increases, the levels of harmful substances in the body increase as well. High levels of these poisons can cause cancer in healthy children, and adult nonsmokers, as well as in smokers themselves.
