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 thousands of harmful chemicals, many of which are known to cause cancer. People who breathe in secondhand smoke can experience health problems, even if they do not smoke themselves. Exposure to secondhand smoke can lead to serious health issues, including respiratory infections, heart disease, and lung cancer. Children and non-smoking adults who are regularly around smokers are particularly at risk. Protecting individuals from secondhand smoke is important for public health and can be achieved through smoke-free policies in places like homes and public spaces.