You don't have to be a smoker for smoking to harm you. You can also have health problems from breathing in other people's smoke. Secondhand smoke is the combination of smoke that comes from the burning end of a cigarette, cigar or pipe and the smoke exhaled by the smoker. Secondhand smoke contains more than 50 substances that can cause cancer. Health effects of exposure to secondhand smoke include lung cancer, nasal sinus cancer, respiratory tract infections and heart disease.

There is no safe amount of secondhand smoke. Children, pregnant women, older people and people with heart or breathing problems should be especially careful.