Cigarettes contains nicotine, a drug that makes smoking highly addictive. In addition to nicotine, tobacco and cigarette smoke contain thousands of other chemicals, many of which are known carcinogens. Cigarette smoking is associated not only with cancer but also with heart disease and a number of other serious illnesses and is, according to the American Heart Association, "the most important preventable cause of premature death in the United States."
Prevalence
In 2008, 46 million adults in the United States were smokers, according to the Centers for Disease Control and Prevention. Smoking is more prevalent in younger age groups---23.7 percent of people ages 25 to 44 are smokers, compared with 9.3 percent of those 65 and older. In 2007, 20 percent of high school students smoked cigarettes.
Toxins
Tobacco and tobacco smoke contain more than 4,000 chemicals, according to the American Cancer Society. These include more than 60 carcinogens. Cigarette smoke also contains ammonia, tar and carbon monoxide. Nicotine is found in all forms of tobacco, including cigarettes, cigars and chewing tobacco.
Cancer
At least 30 percent of all cancer deaths are caused by cigarette smoking, the American Cancer Society estimates. Smoking is linked not only to lung cancer but also to cancers of the oral cavity, larynx, pharynx, esophagus, kidney, bladder, cervix, pancreas and stomach, as well as to acute myeloid leukemia. Almost nine out of every 10 deaths from lung cancer are caused by smoking. Among both men and women, lung cancer kills more people than any other cancer.
Other Health Risks
Cigarette smoking is also associated with heart disease. The main cardiovascular cause of death linked to smoking is atherosclerosis, or the buildup of fatty substances in the arteries. Other cardiovascular risk factors linked to smoking include increased blood pressure, decreased exercise tolerance, increased tendency for blood to clot, and decreased HDL cholesterol, often called "good cholesterol." Smoking increases the risk of recurrent coronary heart disease after bypass surgery and the risks for stroke, peripheral arterial disease and aortic aneurysm. Other health risks associated with smoking include bronchitis, emphysema and worsening of asthma and pneumonia. Smoking can also damage the reproductive health of women.
Death Toll
Of the more than 2.4 million deaths that occur annually in the United States, cigarette smoking is responsible for 440,000---killing more people than suicide, car accidents, AIDS, homicide, alcohol and drugs combined, says the American Cancer Society.
Neuroprotective Effects
Not all news about smoking is bad. Some studies have shown that cigarette smoke may have neuroprotective effects in patients with particular diseases, including schizophrenia and Parkinson's disease. A 2003 study in "The American Journal of Psychiatry" showed that "smoking may be an independent protective factor for developing schizophrenia," although the authors caution that the dangers of smoking far outweigh any possible benefit.
