We know that nicotine and the thousands of toxic chemicals are found in secondhand smoke. Secondhand smoke includes smoke coming directly from the burning tobacco which is called sidestream smoke and smoke exhaled from the tobacco user, called exhaled mainstream smoke. Sidestream smoke has higher concentrations of cancer-causing agents (carcinogens) than mainstream smoke. It also has smaller particles that make their way into the lungs and the body’s cells more easily.
Centers for Disease Control and Prevention (US); National Center for Chronic Disease Prevention and Health Promotion (US); Office on Smoking and Health (US). How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General. Atlanta (GA): Centers for Disease Control and Prevention (US); 2010.