Air pollution is one of the most pervasive environmental problems because
atmospheric currents can carry contaminated air to every part of the globe.
Most air pollution comes, from automobile emissions and from power plants
what burn coal and oil to produce energy for industrial and consumer use. 62. ______
Carbon dioxide and other harmful gases releasing into the air from these 63. ______
sources adversely effect weather patterns and the health of people, animals and . ______
plants.
Industrialized nations produce most of the world’s air pollution. For 65. ______
example, because the United States is home to just 5 percent of the world’s
population, the country generates 22 percent of human-made carbon dioxide 66. ______
emissions or 19 percent of all greenhouse gases such as carbon dioxide and 67. ______
methane. These emissions harm the environment by leading acid rain and
global warming, and by depleting (使衰竭) the protective ozone layer which 68. ______
surround the earth.
Acid rain, a serious threat around the world, occurs when sulfur dioxide
and nitrogen oxide emissions from automobiles and fossil-fuel burning power 69. ______
plants to fall back to Earth as acidic precipitation. Acid rain has contaminated
many lakes in Canada and the northeast United States and has been
documented even in the non-industrial state of Hawaii. In the United 70. ______
Kingdom, 57 percent of all trees are severely defoliated (使落叶) owe to 71. ______
corrosive fallout, and production of food crops has been declined in many parts
of the world. Acid rain has eroded the suces of great art and architectural
treasures, including the ancient sculptures of Rome and the Sphinx in Egypt.