What is second hand smoke, and why do you need to be aware of the dangers?

Second hand smoke is a mixture of smoke from the burning tip of a cigarette (non-filtered), cigar or pipe, and smoke that is breathed out by the smoker. With more than 4000 known substances making up this smoke (including more than 40 known to cause cancer), second-hand smoke (also called environmental tobacco smoke (ETS), is [...]