Environmental Problems, Their Causes, and Sustainability 1

Nasal cavityEpithelial cellCiliaOral cavityMucusPharynx (throat)Trachea (windpipe)BronchusRight lungBronchiolesAlveolar sac(sectioned)BronchioleAlveolar ductAlveoliFigure 20-15 Major components of the human respiratory system.and forth and transport mucus and the pollutants theytrap to your throat (where they are swallowed orexpelled).But prolonged or acute exposure to air pollutantsincluding tobacco smoke can overload or break downthese natural defenses. This can cause or contribute tovarious respiratory diseases. One that can start early inlife is asthma, typically an allergic reaction causing musclespasms in the bronchial walls and acute shortness ofbreath. According to a 2004 report by Harvard MedicalSchool’s Center for Health and the Global Environment,asthma among U.S. preschool children (ages 3 to 5)grew 160% between 1980 and 1994.Years of smoking and breathing air pollutants canlead to other respiratory disorders including lung cancerand chronic bronchitis, which involves persistent inflammationand damage to the cells lining the bronchiand bronchioles. The results are mucus buildup, loud,painful coughing, and shortness of breath. Damagedeeper in the lung can cause emphysema, which is irreversibledamage to air sacs or alveoli leading to loss oflung elasticity and acute shortness of breath (Figure20-16).People with respiratory diseases are especiallyvulnerable to air pollution, as are older adults, infants,pregnant women, and people with heart disease.Figure 20-16 Normal humanlungs (left) and the lungs of a personwho died of emphysema(right). Prolonged smoking and exposureto air pollutants can causeemphysema in anyone, but about2% of emphysema cases resultfrom a defective gene that reducesthe elasticity of the air sacsin the lungs. Anyone with thishereditary condition, for whichtesting is available, should notsmoke and should not live or workin a highly polluted area.O. Auerbach/Visuals Unlimited452 CHAPTER 20 Air Pollution