Scientists now understand the details of how and why smoking is able to exert so many different negative effects on many parts of the body. The smoke from a lighted cigarette contains a mixture of more than 3,000 different substances that are dangerous to living tissue. In addition, tobacco products contain hundreds of chemical additives used as flavors and fillers. No federal agency currently has the authority to require the tobacco industry to reveal the names of these additives, or to remove them from tobacco products if they are found to be harmful. These substances in cigarettes include tars, nicotine, and gases such as carbon monoxide, nitrogen oxide, and hydrogen cyanide. Together, these substances interact to create a huge number of different chemical compounds that have harmful effects on the body. Tobacco tar is made up of hundreds of chemicals that have been shown to cause cancer. Nicotine is the addictive substance in tobacco. The signs of addiction include tolerance (the need to take larger doses to produce the same effects), physical dependence, continued use despite known harmful effects, euphoric effects, relapses following drug abstinence, and recurrent drug cravings. Nicotine is inhaled, along with tars and carbon monoxide, in tobacco smoke. Nicotine in smokeless tobacco is absorbed through the mucous membranes in the mouth (chewing tobacco) or the nose (snuff). Nicotine acts primarily on the nervous system, often causing an increased heart rate and elevated blood pressure. Nearly 90 percent of the nicotine found in cigarettes is inhaled and absorbed into the bloodstream. In addition to its effects on the respiratory system and the gastrointestinal system, nicotine also affects the brain, the spinal cord, and the peripheral nervous system. Nicotine can stimulate, then depress, the production of saliva, constrict the air passages in the lungs, and increase cholesterol levels in the bloodstream. Carbon monoxide is a deadly gas that is a by-product of burning tobacco. It is the same pollutant that is found in automobile exhaust. Carbon monoxide is deadly because it displaces the oxygen molecules in red blood cells, making oxygen less available to your muscles, brain, heart, and other organs. It also damages the lining of arteries, causing atherosclerosis (the buildup of fatty deposits called plaque in the inner lining of the arteries that supply blood to the heart). As a result, the heart must pump harder to deliver an adequate supply of oxygen to the cells. Smokeless Tobacco Smokeless (chewing) tobacco has been making a gradual resurgence in the United States for the past 20 years. Advertisers have presented smokeless tobacco as a healthier alternative to smoking, using the macho image of tobacco-chewing cowboys and athletes to promote their products. Apparently these advertisements have been effective, as indicated by an increase of 52 percent in sales of smokeless tobacco since 1978. It is estimated that 7 million to 11 million Americans, mostly males, use smokeless tobacco. Smokeless tobacco comes in three forms: loose leaf, plugs, and snuff. Chewing tobacco may be packaged as loose-leaf tobacco, which is sold in a pouch. The user places the tobacco between the cheek and the gum, and when a certain amount of tobacco juice and saliva are accumulated in the mouth, it is spit out. Chewing tobacco also can be found as plug tobacco, which is a solid brick form of tobacco. The user cuts off a piece with a knife and chews it, and again, spits it out. Snuff is a finely ground tobacco, sold in cans, that is put on the back of the hand and sniffed through the nose. It also can be placed between the cheek and
the gum. Despite its macho appeal to men, few women find tobacco chewing attractive. Users of smokeless tobacco may not experience the effects of carbon monoxide, but the substance has plenty of other harmful effects, including:
• damage to the soft and hard tissues in the mouth
• excessive abrasion of tooth surfaces
• presence of nitrosonornicotine, a cancer-causing agent
• increase in heart rate and blood pressure
• development of leukoplakia, a disease that results in thick, white patches on the cheek, tongue, and other parts of the mouth
• cancer of the inner lining of the cheek
• suppressed immune response
• increase in the number of dental cavities
• inflammation of the gums
• cancers of the pharynx, esophagus, bladder, and pancreas
• darkened teeth and bad breath
Secondhand Smoke Breathing in smoke from someone else’s tobacco presents a significant risk to a nonsmoker’s health. Exposure to so-called secondhand smoke (sometimes referred to as passive smoking) is a significant cause of heart disease, stroke, lung cancer, and respiratory problems such as bronchitis. Two different types of smoke enter the air when a person smokes: exhaled smoke and the smoke that comes directly from the burning tobacco. This second, more dangerous type of smoke is what hovers in the air in smoke-filled rooms. Secondhand smoke is especially harmful to infants and young children. Smoking by parents is known to worsen asthma in children and even to trigger asthma attacks. Children without asthma whose parents smoke have far more respiratory illnesses coughs, colds, middle ear infections, pneumonia, and bronchitis than children of nonsmokers.
