Smoking, inhalation and exhalation of the fumes of burning tobacco. Leaves of the tobacco plant are smoked in various ways. After a drying and curing process, they may be rolled into cigars or shredded for insertion into smoking pipes. Cigarettes, the most popular method of smoking, consist of finely shredded tobacco rolled in lightweight paper. About 46 million people in the United States smoke an estimated 420 billion cigarettes each year. Nicotine has various effects on the body. In small doses nicotine serves as a nerve stimulant, entering the bloodstream and promoting the flow of adrenaline, a stimulating hormone. It speeds up the heartbeat and may cause it to become irregular. It also raises the blood pressure and reduces the appetite, and it may cause nausea and vomiting. The known health risks associated with cigarette smoking, such as damage to the lungs and lung cancer, are thought to be caused by other components of cigarettes such as tars and other by-products of smoking, and by the irritating effects of smoke on the lung tissue. Addiction to smoking is caused by nicotine itself. Stopping smoking produces withdrawal symptoms within 24 to 48 hours, which commonly include irritability, headaches, and anxiety, in addition to the strong desire to smoke.





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