The respiratory system can be damaged by a variety of chemicals found in the environment, ranging from automobile fumes and industrial smoke to household cleaning products. Cigarette smoke, however, poses a particularly serious threat to the respiratory system because of the tar and other substances that enter the lungs. After a person smokes just one cigarette, for example, tar temporarily paralyzes the cilia of the upper and lower respiratory tracts.
The tar also temporarily immobilizes the macrophages in the alveoli of the lungs. With the filtering and cleansing functions inactivated, the air passages and lungs are exposed not only to the irritating effects of tar but also to airborne bacteria, viruses, and other particles. These, along with the tar, settle in the mucous layers of the lungs. The paralyzed cilia recover after about one hour, but repeated smoking eventually kills them. Repeated smoking also causes mucus to build up in the lungs and block the smaller air passages. The blockage triggers a cough reflex—the familiar “smoker’s cough”—the lung’s effort to clear the airways. In addition, tobacco smoke contains over 40 chemicals known to cause cancer. Smoking is responsible for almost 90 percent of lung cancer cases among men, and more than 70 percent among women.
Workers in occupations that produce impurities released into the air are at high risk for respiratory illnesses. Sandblasters, stone cutters, quarry workers, miners, construction workers, people who install brake lining or insulation, people who work in shipyards or on farms, and people who pick cotton are among those at risk. In the United States, the Occupational Safety and Health Administration (OSHA) issues regulations that protect workers—requiring air masks with filters for certain jobs, for example. The Environmental Protection Agency (EPA) monitors and regulates the amount of pollutants released into the air. Despite these efforts, respiratory illnesses remain higher among workers who have significant exposure to air pollutants.
Normal, everyday exposure to air pollution from cars and industrial emissions in the city also weakens the respiratory system of city-dwellers. Even if a person does not smoke, the city air gradually changes pink, healthy lung tissue to tissue darkened with particles of smog, dust, and other pollutants, making the lungs more vulnerable to infection. While outdoor pollutants pose threats to the respiratory system, a far greater threat is created by indoor air pollution. In homes and offices, a variety of substances, including cleaning compounds, air fresheners, synthetic carpets and furniture, and certain construction materials, can emit hazardous gases, which become highly concentrated in unventilated rooms. Individuals at greatest risk are those who spend most of their time indoors, children, the elderly, and people with a history of respiratory illnesses. Like outdoor air pollutants, indoor air pollutants weaken the lungs and invite infection. The long-term effects of air pollution are difficult to measure, but may include cancer and other serious diseases.