TOBACCO AND ITS EFFECTS

The chemical stimulant nicotine is the major psychoactive substance in all tobacco products. In its natural form, nicotine is a colorless liquid that turns brown upon oxidation (exposure to oxygen). When tobacco leaves are burned in a cigarette, pipe, or cigar, nicotine is released and inhaled into the lungs. Sucking or chewing a quid (a pinch of snuff typically tucked between the gum and lower lip) of tobacco releases nicotine into the saliva, and the nicotine is then absorbed through the mucous membranes in the mouth.

Smoking is the most common form of tobacco use. Smoking delivers a strong dose of nicotine to the user, along with an additional 4,000 chemical substances. Among these chemicals are various gases and vapors that carry particulate matter in concentrations that are 500,000 times greater than those of the most air-polluted cities in the world.

Particulate matter condenses in the lungs to form a thick, brownish sludge called tar. Tar contains various carcinogenic (cancer-causing) agents such as benzo(a)pyrene and chemical irritants such as phenol. Phenol has the potential to combine with other chemicals to contribute to the development of lung cancer.

In healthy lungs, millions of tiny hair-like tissues called cilia sweep away foreign matter. Once the foreign material is swept up and collected by the cilia, it can be expelled from the lungs by coughing. Nicotine impairs the cleansing function of the cilia by paralyzing them for up to one hour following the smoking of a single cigarette. Tars and other solids in tobacco smoke are thus allowed to accumulate and irritate sensitive lung tissue.

Tar and nicotine are not the only harmful chemicals in cigarettes. In fact, tars account for only 8 percent of the components of tobacco smoke. The remaining 92 percent consists of various gases, the most dangerous of which is carbon monoxide. In tobacco smoke, the concentration of carbon monoxide is 800 times higher than the level considered safe by the U.S. Environmental Protection Agency (EPA). In the human body, carbon monoxide reduces the oxygen-carrying capacity of the red blood cells by binding with the receptor sites for oxygen. Smoking thus diminishes the capacity of the circulatory system to carry oxygen, causing oxygen deprivation in many body tissues.

The heat from tobacco smoke, which can reach 1,616 degrees Fahrenheit, is also harmful to the smoker. Inhaling hot gases and vapors exposes sensitive mucous membranes to irritating chemicals that weaken the tissues and contribute to the development of cancers of the mouth, larynx, and throat.

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