HEALTH EFFECTS OF SMOKING

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.

Smoking accounts for nearly 90 percent of lung cancer deaths. Additionally, smokers are at increased risk for cancer of the larynx, oral cavity, esophagus, bladder, kidney, and pancreas. While some negative health effects of smoking manifest slowly over time, others can be measured almost immediately. Sticky brown tar leaves yellow stains on fingers and teeth. Some of the inhaled tar is absorbed by lung cells, causing them to die. Tar also damages the cilia in the upper airways that protect against infection. Nicotine causes arteries to constrict, lowering skin temperature and reducing blood flow to the hands and feet. Carbon monoxide deprives the body of oxygen, binding to red blood cells in place of the oxygen molecule and forcing the heart to pump more blood through the body.

One-third of smoking-related deaths are caused by coronary heart disease or chronic airway obstruction. For example, the nicotine in tobacco combines with carbon monoxide in tobacco smoke to damage the lining of blood vessels and make blood platelets stickier. Platelets form part of the damaging plaque buildup in artery walls. These effects in combination contribute to the development of heart disease. Smoking also increases the risk of stroke by 50 percent—40 percent among men and 60 percent among women. Other research has shown that mothers who smoke give birth more frequently to premature or underweight babies, probably because of a decrease in blood flow to the placenta. Babies born to mothers who smoke during pregnancy are also at increased risk for sudden infant death syndrome.

Cigar and pipe smoke contains the same toxic and carcinogenic compounds found in cigarette smoke. A report by the National Cancer Institute concluded that the mortality rates from cancer of the mouth, throat, larynx, pharynx, and esophagus are approximately equal in users of cigarettes, cigars, and pipes. Rates of coronary heart disease, lung cancer, emphysema, and chronic bronchitis are elevated for cigar and pipe smokers and are correlated to the amount of smoking and the degree of inhalation.

Studies have found that cigarettes are addictive because an unknown component of tobacco smoke appears to destroy an important brain enzyme known as monoamine oxidase B (MAO B). The enzyme is vital for breaking down excess amounts of dopamine, a neurotransmitter that triggers pleasure-seeking behavior. Smokers have decreased levels of MAO B and abnormally high levels of dopamine, which may encourage the smoker to seek the pleasure of more tobacco smoke.

Even nonsmokers are at risk from smoking. Recent research has focused on the effects of environmental tobacco smoke (ETS)—that is, the effect of tobacco smoke on nonsmokers who must share the same environment with a smoker. The United States Environmental Protection Agency (EPA) estimates that exposure to ETS, which contains all the toxic agents inhaled by a smoker, causes 3,000 lung cancer deaths and an estimated 35,000 deaths from heart disease per year among nonsmokers. Secondhand smoke can aggravate asthma, pneumonia, and bronchitis, and impair blood circulation.

The smoking habit and addiction to nicotine usually begin at an early age. In the United States, more than 90 percent of adults who smoke started by age 21, and nearly half of them were regular smokers by the age of 18. Despite increasing warnings about the health hazards of smoking and widespread bans on smoking in public places, smoking remains common among teenagers and young adults. In 2001 surveys of students in grades 9 through 12 found that more than 38 percent of male students and nearly 30 percent of female students smoke. Although black teenagers have the lowest smoking rates of any racial group, cigarette smoking among black teens increased 80 percent in the late 1990s. Advertisements aimed at a young audience are largely blamed for this new generation of smokers.