Pollution of the environment occurs when humans contaminate the air, water, or land. Pollution can also be broken down into two categories: primary and secondary. Primary pollution is when humans directly contaminate the earth in some manner. Examples include mercury, sulfur, and even carbon dioxide. Secondary pollution happens when a primary pollutant reacts with another primary pollutant, sunlight, and water to create a different pollutant.

An example is acid rain. Sulfur dioxide is a primary pollutant, but when it reacts with precipitation is becomes a secondary pollutant called acid rain. One of the biggest problems with pollution is that those who pollute are usually not the ones affected by it; instead, the down-winders are.

Air Pollution

The atmosphere is mostly made of 78 percent nitrogen, 21 percent oxygen, and small percents of other trace molecules such as ozone, carbon dioxide, water vapor, and aerosols. Air pollution occurs when humans add unnatural substances into the atmosphere. Most of the air pollution from the industry comes from coal, while automotive pollute vast amounts of ozone, carbon dioxide, and sulfur into the atmosphere. However, in the 1970s, the United States created the Clean Air Act, which has dramatically enhanced the quality of our nation’s air. Check out this video from National Geographic on the world’s air quality.

Those who pollute are usually not the ones affected by it. Industrialization in eastern North American and eastern Europe have generated large-scale pollutants such as sulfur oxides and nitrogen oxides through the burning of fossil fuels. When these pollutants react with water, they form acid precipitation. Acid precipitation can cause large-scale damage to aquatic life and forests by making the vegetation very sick and dying. In forests, this can lead to disease through pest infestation. Acid precipitation can also damage or destroy buildings and monuments made out of marble such as tombstones.

Ozone Hole

In the 1920s, humans developed a chemical called chlorofluorocarbons (CFCs) for things such as refrigerating and air conditioners. However, in the 1970s, two American scientists discovered that these CFCs were weakening the ozone hole. What they learned is that when the CFC’s reach the layer of the ozone hole, the ultraviolet radiation from the sun breaks the chlorine off which can attach and destroy over 100,000 ozone molecules and continue in the upper atmosphere for over 100 years. Over time and much debate, the world got together and signed the Montreal Protocol in 1987 to phase out CFCs. Today, most industrialized countries have eliminated the use of CFCs, but the ozone hole is not required to heal for another 50-100 years. Learn more about what is currently going on with the ozone hole at NASA’s Ozone Hole Watch.

Water Pollution

Water is the most valuable resource on the planet, but humans keep polluting it in various ways. Manufactures use water to create and process food. Farmers pollute vast amounts of water through fertilizer and waste from pigs and cows in unhealthy feedlots. Water is used by coal powerplants to extract and wash coal, along with cooling the steam used to make electricity. All of these processes, along with residential use, have negative impacts on water quality.

Water pollution can significantly harm aquatic life in rivers, lakes, and the ocean. Many of the fertilizers in farmers and the cleaners we use can create algae blooms in our local rivers. When the algae die, it can also remove the oxygen from the water, which can kill fish and other aquatic life. These are called dead zones, and one of the biggest in the world is forming in the Gulf of Mexico because of the pollution in the Mississippi River. Just like our air, the nation’s water has dramatically improved since the 1970s because of the Clean Water Act.

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