Environmental Chapter 2.doc

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Environmental Science
Zachariah Campbell

Environmental Chapter 2: Urban and T ransboundary Air Pollution • Much of what we currently understand about environmental lung disease derives from the study of exposed workers since the Industrial Revolution • Recognition of the relationship between nonworkplace air pollution and respiratory disease dates back to the first use of coal as a combustion source in the 14 century -air pollution emergencies were caused by ait stagnation, which resulted in greatly increased concentrations of atmospheric pollutants, especially sulphur dioxide and suspended particulates -worst episode occurred in London, where number of deaths reached 4000 • Since the atmosphere is dynamic and always changing, contaminants are transported, diluted, precipitated, and transformed • Air pollution knows no boundaries or nation borders • Primary emissions of sulphur oxides, nitrogen oxides, carbon monoxide, respirable particulates, and metals are severely pollution cities and towns in Asia, Africa, Latin America, and Eastern Europe • Relationship between air pollution and wealth; poorer countries (relying heavily on coal) had significantly higher levels of total suspended particulates (TSPs) than wealthier nations • In nations that have reduced the primary emissions from heavy industry, power plants, and automobiles, new problems have arisen from pollution by newer industries and from air pollution caused by secondary formation of acids and ozone -the resulting high levels of air pollution (including indoor air pollution) contribute heavily to the high mortality rates observed for acute respiratory disease in children under the age of 5 in many developing countries Defining Adverse Health Effects • Adverse health effect; any effect that results in altered structure or impaired function that represents the beginning of a sequence of events leading to altered structure or function Specific Air Pollutants Associated with Adverse Respiratory Effects • TABLE 2.1 Sulfur Dioxide and Acidic Aerosols • Major sources of environmental pollution with sulphur dioxide are electric power generating plants, oil refineries, and smelters • Some fuels such as ‘soft’ coal are particularly sulphur-rich • Sulphur dioxide released into the atmosphere does not remain gaseous; it undergoes chemical reaction with water, metals, and other pollutants to form aerosols • Most common pollutants resulting from this atmospheric reaction are sulphuric acid, metallic acids, and ammonium sulphates • Smog; refers to the visibly cloud combination of smoke and fog • Higher particle acidity was significantly associated with an inc Particulates • Particulate; particles suspended in the air after various forms of combustion or other industrial activity • ‘fine’ particles produced almost exclusively from combustion sources have been closely studied under the hypothesis that such small particles can penetrate deeply into the lung, while larger particles would be trapped in the upper airway • Heart-rate variability (HRV); a measure of the cyclic variations of beat-to-beat intervals and of the instantaneous heart rate -evidence that reduced HRV is a risk factor for adverse cardiac events, including angina, myocardial infarction (MI), life threatening arrhythmias, and congestive heart failure • Very high particulate levels measured in developing countries range up to 100 times the current US standard • Deaths in children from acute respiratory disease are high when particulate levels are high, even in nations with lower overall infant mortality • After infant diarrhea, acute respiratory disease is believed to be the major cause of death in children under the age of five in the developing world and to account for up to 4 million fatalities per year -air pollution plays a central role in this epidemic Photochemical Oxidants • Other two most commonly generated industrial and urban pollutants are ozone and oxides of nitrogen -produced not so much by heavy industry and by the action of sunlight on the waste products of the internal combustion engine • The most important of these products are unburned hydrocarbons and nitrogen dioxide, a product of the interaction of atmospheric nitrogen with oxygen during high-temperature combustion • Mixture of pollutants constitutes the smog that has become associated with cities with ample sunlight • Ozone and ni
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