While some natural forces may pollute the air, air pollution is primarily caused by humans. Air pollution releases deadly contaminants into the atmosphere that can affect the land and all life on the planet. Air pollution is mobile, so that even areas far from its source may be affected, further complicating the issue.
Effects on Plant Life
Air pollution harms the plant life by disrupting photosynthesis. A study published in the journal Cellular and Molecular Life Sciences found that air pollution reduces the size of a plant's stomata or pores. These pores are located on plant leaves and are the sites of gas exchange. A reduction in size lowers the amount of carbon dioxide a plant can receive, a vital ingredient for photosynthesis or food and energy production. If photosynthesis slows, plant growth declines as well. A 2005 study published in Encyclopedia of Plant and Crop Science confirmed these findings, further reporting that pollutants such as ozone will harm plants.
Acid rain is especially dangerous in that it harms not only the air, but also pollutes water and soils. Acid rain forms when sulfur dioxide combines with moisture in the air, creating the acidic precipitation. Acid rain falling on the land will acidify soils and water. Left unchecked, the resources become ecological dead zones because of the acidic conditions, unable to support any life forms.
Sources of Air Pollution
Most of the most toxic air pollutants come from fossil fuel emissions, whether it is from a coal-burning power plant or from automobile exhaust. These emissions contain sulfur dioxide, nitrogen oxide and carbon dioxide. Other industries also introduce toxins into the air. Hydrogen fluoride emissions occur during phosphate fertilizer production. This contaminant is especially dangerous because it can cause a slowing of photosynthesis even at low concentrations. Its presence also alters soil chemistry.
Pollution in the form of dust or particulate matter can harm the land and its people. Particulate matter enters the air in several ways, such as the burning the wood and other fuels. In high concentrations, it can reduce visibility not only in cities, but also in wilderness areas. The U.S. Environmental Protection Agency (EPA) and other agencies monitor air quality through its Regional Haze Program.
Federal and state regulations have reduced some forms of air pollution. According to the EPA, sulfur dioxide emissions are down more than 70 percent from 1980 to 2008, diminishing the effects of some environmental problems such as acid rain. However, while sulfur dioxide emissions are down, total emissions overall increased from 1990 to 2008 by 14 percent.