Read the following passage & mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to lớn each of the questions from 1 to lớn 10.

Bạn đang xem: What is air pollution

A useful definition of an air pollutant is a compound added directly or indirectly by humans to lớn the atmosphere in such quantities as lớn affect humans, animals, vegetations, or materials adversely. Air pollution requires a very flexible definition that permits continuous change. When the first air pollution laws were established in Englvà in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled-a far cry from the extensive menu of harmful substances known today. As technology has developed và knowledge of the health aspects of various chemicals has increased, the menu of air pollutants has lengthened. In the future, even water vapor might be considered an air pollutant under certain conditions.Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, & nitrogene oxides, are found in nature. As the Earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycles. These serve as an air purification scheme by allowing the compounds to move from the air to lớn the water or soil on a global basis, nature"s output of these compounds dwarfs that resulting from human activities. However, human production usually occurs in a localized area, such as a city.In this localized regions, human output may be dominant and may temporarily overload the natural purification scheme of the cycle. The result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance lớn be a pollutant; in fact the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0.08 parts per million (ppm), which is about 400 times its natural cấp độ. Carbon monoxide, however, as a natural màn chơi of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.


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A. The economic impact of air pollution