Nicotine is a drug found in the leaves of the tobacco plant. It is consumed by smoking cigarettes, pipes, or cigars or by using smokeless tobacco. Nicotine stimulates the central nervous system and increases heart rate and blood pressure, lowers skin temperature, and makes the user breathe faster. This can cause fatigue, lowered physical endurance, shortness of breath, heart palpitations, and stress on the heart.

Because nicotine can act as either a sedative or stimulant, its emotional effects include relaxation as well as irritability and nervousness. Nicotine is a highly addictive drug, both physically and psychologically. The long-term consequences of tobacco use include lung and respiratory damage, muscle wasting, peptic ulcer disease, cancer, and cardiovascular disease.

Non-smokers can be exposed to the harmful effects of tobacco by inhaling side-stream smoke from the lighted tips of cigarettes, cigars, and pipes. Side-stream smoke (also known as passive, second-hand, or environmental smoke) has immediate and long-term effects on those who breathe it.

Non-smokers often suffer from eye irritation, headaches, nose and throat discomfort, and allergic reactions when exposed to side-stream smoke. Side-stream smoke increases the risk of lung cancer among non-smokers by as much as 34 percent. Non-smokers who live with smokers are also more likely than other people to develop heart disease and breast, cervical, and nasal/sinus cancer. For example, an estimated 53,000 Americans die annually from the effects of side-stream smoke, making it the third leading cause of death after active tobacco and alcohol use.