Tobacco is a substance legally sold in products such as cigarettes, cigars, and smokeless tobacco (pipes, snuff, chew/spit tobacco). Nicotine, the active ingredient in tobacco products, is one of more then 4,000 chemicals found in tobacco smoke. Researchers have identified more than 250 chemicals in tobacco smoke that are toxic or cause cancer in humans and animals. Smokeless tobacco products such as snuff and chewing tobacco also contain high levels of nicotine as well as other toxins.
Nicotine is absorbed readily from tobacco smoke in the lungs, and it does not matter whether the tobacco smoke is from cigarettes, cigars, or pipes. Nicotine also is absorbed readily when tobacco is chewed. With regular use of tobacco, levels of nicotine accumulate in the body during the day and persist overnight. Thus, daily smokers or chewers are exposed to the effects of nicotine for 24 hours each day. Nicotine taken in by cigarette or cigar smoking takes only seconds to reach the brain but has a direct effect on the body for up to 30 minutes. Tobacco use is the leading preventable cause of death in the United States, killing more people than alcohol, cocaine, heroin, homicide, suicide, car accidents, fire and AIDS combined.