"Tobacco products contain more than 4,000 chemicals, some of which could contribute to dependence. However, there is little debate that nicotine is a major tobacco component responsible for addiction (USDHHS 1988; Stolerman and Jarvis 1995; Royal College of Physicians of London 2000; Balfour 2004)."
Source
US Department of Health and Human Services. "How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General." Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2010, p. 111.
http://www.cdc.gov/tobacco/da…
