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Pollutant Populations at Risk EffectsOzone Healthy adults and children Decreased lung function Increased airway reactivity Lung inflammation Athletes, outdoor workers Decreased exercise capacity Asthmatics Increased hospitalizations Nitrogen dioxide Healthy adults Increased airway reactivity Asthmatics Decreased lung function Children Increased respiratory infections Sulfur dioxide Healthy adults Increased respiratory symptoms Patients with chronic lung disease Increased mortality Increased hospitalization Asthmatics Decreased lung function Acid aerosols Healthy adults Altered mucociliary clearance Children Increased respiratory infections Asthmatics Decreased lung function Increased hospitalizations Particulates Children Increased respiratory infections Decreased lung function Patients with chronic lung or heart disease Excess mortality Asthmatics Increased attacks Data from Bascom R, et al: Health effects of outdoor air pollution, Am J Respir Crit Care Med 153:3, 477, 1996. cause increased epithelial permeability and reactivity of the airways, and decrease ciliary clearance. The highest inhaled dose is delivered at the bronchoalveolar junction; however, ozone also causes inflammation of the upper respiratory tract. Nitrogen Dioxide. Oxides of nitrogen include NO and NO2 . These have lower reactivity than ozone. Nitrogen dioxide dissolves in water in the airways to form nitric and nitrous acids, which damage the airway epithelial lining. Children and patients with asthma have increased susceptibility to nitrogen dioxide; there is a wide variation in individual responses to this pollutant. Sulfur Dioxide. This pollutant is highly soluble in water; it is absorbed in the upper and lower airways, where it releases H+ , HSO3 - (bisulfite), and SO3 - (sulfite), which cause local irritation. Acid Aerosols. Primary combustion products of fossil fuels are emitted by tall smoke stacks at high altitudes and are transported by air. In the atmosphere, sulfur and nitrogen dioxide are oxidized to sulfuric acid and nitric acid, respectively, which are dissolved in water droplets or adsorbed to particulates. These acid aerosols are irritants to the airway epithelium and alter mucociliary clearance. Asthmatics have decreased lung function and increased hospitalizations when exposed to acid aerosols, although there is a wide variation in airway responses. Particulates. As discussed in Chapter 15 , the deposition and clearance of particulates inhaled into the lungs depend on their size. Ambient particulates are highly heterogeneous in size and in chemical composition. It is uncertain which characteristics of ambient particulates contribute to their adverse health effects. Recent epidemiologic and toxicologic studies suggest that ultrafine particles (less than 0.1 μm in aerodynamic diameter) are more hazardous. They contribute to increased morbidity and mortality, especially among infants, the elderly, and people with chronic cardiopulmonary disease. The mechanisms responsible for these adverse health effects are suspected to involve: (1) systemic cytokine release associated with pulmonary inflammation; (2) increased blood viscosity; and (3) autonomic changes associated with variable heart rates and arrhythmias.[35] Date: 2016-04-22; view: 764
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