Secondhand Smoke comes from lit cigarettes and cigars. It also comes from smoke breathed out by smokers. When children breathe secondhand smoke, it is like they are smoking, too. Secondhand smoke is made of thousands of chemicals. Many are poisons that stay in your body.
Exposure to secondhand smoke contributes to approximately 41,000 deaths among nonsmoking adults and 400 deaths in infants each year. Secondhand smoke causes stroke, lung cancer, and coronary heart disease in adults. Children who are exposed to secondhand smoke are at increased risk for sudden infant death syndrome, acute respiratory infections, middle ear disease, more severe asthma, respiratory symptoms, and slowed lung growth. (CDC.gov)