The leaf of several species of nicotiana, especially of the American plant Nicotiana tabacum. The smoking of tobacco is the most serious public-health hazard in the World. It causes about 100,000 deaths a year in England alone, and 6 million people worldwide.. The most frequent causes of death are lung CANCER, CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) and CORONARY heart disease. It is also a major cause of disability and illness in the form of PERIPHERAL VASCULAR DISEASE. Also, smokers have more persistent or more severe colds, CROHN'S DISEASE, INFLUENZA, TUBERCULOSIS and ASTHMA. They have worse symptoms than non-smokers for conditions such as chronic RHINITIS, diabetic eye disease (see DIABETES MELLITUS), HYPERTHYROIDISM, MULTIPLE SCLEROSIS (MS) and OPTIC NEURITIS. Apart from lung cancer, smoking increases the risk of cancer of the larynx, mouth, oesophagus, bladder, pancreas, kidney, liver, bowel, cervix and ovary. Smokers are less fertile than non-smokers and have a greater prevalence of impotence, erectile dysfunction and disease of the gums and teeth. Tobacco-smoking is also a hazard to the FETUS if the mother smokes. Worldwide, half of long-term smokers will die prematurely because of their habit and half of those die before they are 70. Furthermore, passive smoking – inhalation of other people's tobacco smoke – has been shown to be a health hazard to non-smokers.
Tobacco leaves contain various organic constituents including NICOTINE. It is this substance that causes a person to become habituated to tobacco smoking (see DEPENDENCE).
Tobacco smoke also contains some 16 substances capable of inducing cancer in experimental animals. One of the most important of these is benzpyrene, a strongly carcinogenic hydrocarbon. As this is present in coal tar pitch, it is commonly referred to in this context as tar. Other constituents of tobacco smoke include pyridine, ammonia and carbon monoxide.
Measures such as banning smoking in public places, restricting advertising and sponsorship, increasing tax on tobacco and urging substituting with electronic cigarettes, along with health education generally are all used to try to reduce the health risks from tobacco.