Secondhand smoke is the smoke that comes from burning tobacco products, such as cigarettes and cigars, as well as the smoke exhaled by smokers. It contains a mixture of over 7,000 chemicals, many of which are toxic and can cause serious health problems. People who breathe in secondhand smoke can experience immediate effects, such as eye irritation and coughing. Exposure to secondhand smoke is particularly harmful to vulnerable groups, including children and pregnant women. It can lead to respiratory issues, increased risk of asthma, and even sudden infant death syndrome (SIDS). Reducing exposure to secondhand smoke is important for public health.