Pollution and Acid Rain — Reading Comprehension Lesson

Reading Passage

Pollution and Acid Rain

Pollution occurs when harmful substances enter the environment in quantities that damage living things or natural systems. Air pollution is one of the most widespread forms of environmental damage. It is caused primarily by the burning of fossil fuels — coal, oil, and natural gas — in power plants, factories, and vehicles. The combustion of these fuels releases sulfur dioxide and nitrogen oxides into the atmosphere, along with particulate matter, carbon monoxide, and other pollutants that harm human health and the environment.

Acid rain is one of the most serious consequences of air pollution. When sulfur dioxide and nitrogen oxides are released into the atmosphere, they react with water vapor, oxygen, and other chemicals to form sulfuric acid and nitric acid. These acids fall to Earth as rain, snow, sleet, or fog — a phenomenon called acid deposition. Normal rainwater is slightly acidic, with a pH of about 5.6, but acid rain can have a pH as low as 4.2 — about the acidity of orange juice. Acid deposition can fall far from its source: pollution from industrial regions in the American Midwest affects ecosystems in New England and eastern Canada.

Acid rain causes severe damage to aquatic ecosystems. As acids accumulate in lakes and streams, water pH drops, making the water inhospitable to fish, amphibians, and aquatic insects. Many lakes in the northeastern United States and Scandinavia became nearly lifeless during the height of the acid rain problem in the 1970s and 1980s. Acid rain also damages forests by leaching nutrients from soil and weakening trees, making them more vulnerable to disease, insects, and extreme weather. It dissolves limestone and marble in buildings, bridges, and historic monuments.

International efforts to reduce acid rain have had significant success. In the United States, the Clean Air Act of 1970 and its amendments in 1990 established caps on sulfur dioxide and nitrogen oxide emissions from power plants. The use of scrubbers — devices that remove sulfur dioxide from power plant exhaust before it reaches the atmosphere — reduced emissions dramatically. As a result, acid rain levels in the eastern United States have declined significantly since their peak. However, acid rain remains a serious problem in parts of Asia, where coal use has expanded rapidly.

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