SMOKING

Smoking is the primary cause of chronic obstructive pulmonary disease such as emphysema and chronic bronchitis. Deaths caused by emphysema and chronic bronchitis are significantly more frequent than among nonsmokers.

Tobacco smoke contains a mixture of chemicals, gases, and tiny droplets of tar. Thousands of substances have been identified in tobacco smoke. The toxic effects of many of them remain unknown. Some components are filtered off when the person draws the smoke through the remaining unburned tobacco. However, as the cigarette burns, these chemicals are vaporized again and each puff of smoke thus contains more of the components. Most smokers inhale the cigarette smoke, which makes it even more dangerous.

Cigarette smoke contains 2 to 6 percent carbon monoxide. Carbon monoxide is a toxic gas that combines with hemoglobin (carboxyhemoglobin). When this occurs the hemoglobin molecule cannot transport oxygen to the tissues. Many smokers have carboxyhemoglobin levels of 8 to 10 percent in their blood whereas a nonsmoker commonly has only up to 1.5 percent. A person dying from acute carbon monoxide poisoning has blood carboxyhemoglobin levels of 30 to 40 percent. Thus, the tissues are deprived of needed oxygen.

The tar found in cigarettes contains substances that cause cancer. Irritants in tobacco smoke cause the person’s air passages to constrict and bronchial tubes to produce excess mucus, and they cause the person to cough. These irritants also may impair the function of the immune system cells in the lungs and upset the normal balance of pulmonary enzymes, which makes the person more susceptible to respiratory disease. Finally, inhaled tobacco smoke stops the action of the cilia in the airway. Cilia are tiny hair-like projections in the trachea and bronchial tubes. They help expel foreign material from the lungs.

Thus, the main health risks in tobacco pertain to diseases of cardiovascular system, in particular myocardial infarction, diseases of respiratory system, and cancer, particularly lung cancer and cancers of the larynx and tongue. A person’s increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heart disease is half that of a continuing smoker.