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Air pollution
 
Environmental Pollution
Types of pollution
Air pollution
Water pollution
Soil pollution
Controlling pollution
Government action
Scientific efforts
Business and industry
Agriculture
Environmental organizations
History
The growth of pollution
Progress in controlling pollution
Current environmental issues
 
The Clean Development Mechanism
Global warming
Reducing emissions (REDD)
Swine Influenza
Cholesterol
Heart Attack
 

Types of pollution

The chief types of environmental pollution include air pollution, water pollution, soil pollution, pollution caused by solid waste and hazardous waste, and noise pollution.

Air pollution

Air pollution is the contamination of the air by such substances as fuel exhaust and smoke. It can harm the health of plants and animals and damage buildings and other structures. It can potentially cause a change in the worldwide climate. According to the World Health Organization, about 3 million people die each year as a result of air pollution.

The atmosphere normally consists of nitrogen, oxygen, and small amounts of carbon dioxide and other gases and particulates (tiny particles of liquid or solid matter). A number of natural processes work to keep the parts of the atmosphere in balance. For example, plants use carbon dioxide and produce oxygen. Animals, in turn, use up oxygen and produce carbon dioxide through respiration. Forest fires and volcanic eruptions shoot gases and particulates into the atmosphere, and rain and wind wash them out or scatter them.

Air pollution occurs when industries and vehicles release such large amounts of gas and particulates into the air that natural processes can no longer keep the atmosphere in balance. There are two chief types of air pollution: (1) outdoor and (2) indoor.

Outdoor air pollution. Each year, hundreds of millions of tons of gases and particulates pour into the atmosphere. Most of this pollution results from the burning of fuel to power motor vehicles and to heat buildings. Some air pollution also comes from business and industrial processes. For example, many dry cleaning plants remove dirt from clothing with a chemical called perchloroethylene, which is a hazardous air pollutant. The burning of garbage may discharge smoke and heavy metals, such as lead and mercury, into the atmosphere. Most heavy metals are highly poisonous.

One of the most common types of outdoor air pollution is smog. Smog is a brown, hazy mixture of gases and particulates. It develops when certain gases released by the combustion of gasoline and other petroleum products react with sunlight in the atmosphere. This reaction creates hundreds of harmful chemicals that make up smog.

One of the chemicals in smog is a toxic form of oxygen called ozone. Exposure to high concentrations of ozone causes headaches, burning eyes, and irritation of the respiratory tract in many individuals. In some cases, ozone in the lower atmosphere can cause death. Ozone can also damage plant life and even kill trees.

Particulates can also contribute to air pollution. Some particles of fossil fuels escape boilers in factories and engines in cars and trucks without undergoing complete combustion (burning). These particles pollute in many ways. They fall onto vegetation and the surfaces of buildings, dirtying them. Particulates can mix with other chemicals to create smog. They can also enter people's lungs and cause asthma or other diseases.


Acid rain is a term for rain and other precipitation that is polluted mainly by sulfuric acid and nitric acid. These acids form when gases called sulfur dioxide and nitrogen oxides react with water vapor in the air. These gases come chiefly from the burning of coal, gas, and oil by cars, factories, and power plants. The acids in acid rain move through the air and water and harm the environment over large areas. Acid rain has killed entire fish populations in a number of lakes. It has also damaged many buildings, bridges, and statues. Scientists believe high concentrations of acid rain can harm forests and soil. Regions affected by acid rain include large parts of eastern North America, Scandinavia, and central Europe.

Chemicals called chlorofluorocarbons (CFC's) are pollutants that destroy the ozone layer in the upper atmosphere. CFC's have been used as refrigerants in air conditioners and refrigerators and to make plastic foam insulation. Ozone, the same gas that is a harmful pollutant in smog, forms a protective layer in the upper atmosphere. It shields Earth's surface from more than 95 percent of the sun's ultraviolet radiation. As CFC's thin the ozone layer, more ultraviolet radiation reaches the surface of Earth. Overexposure to such radiation damages plants and greatly increases people's risk of skin cancer.

The greenhouse effect is the warming that results when Earth's atmosphere traps the sun's heat. It is created by carbon dioxide, methane, and other atmospheric gases, which allow sunlight to reach Earth but prevent heat from leaving the atmosphere. These heat-trapping gases are often called greenhouse gases.

Fuel burning and other human activities are increasing the amount of greenhouse gases in the atmosphere. Many scientists believe such an increase is intensifying the greenhouse effect and raising temperatures worldwide. This increase in temperature, called global warming, may cause many problems. A strong greenhouse effect could melt glaciers and Arctic ice, flooding coastal areas. It could also shift rainfall patterns, creating more droughts and severe tropical storms.

Indoor air pollution occurs when buildings with poorly designed ventilation systems trap pollutants inside. The main types of indoor pollutants are tobacco smoke, gases from stoves and furnaces, household chemicals, small fiber particles, and hazardous fumes given off by building materials, including insulation, glue, and paint. In some office buildings, high amounts of these substances cause headaches, eye irritation, and other health problems in workers. Such health problems are sometimes called sick building syndrome.

Radon, a radioactive gas given off through the decay of uranium in rocks within Earth, is another harmful indoor pollutant. It can cause lung cancer if inhaled in large quantities. People can be exposed to radon when the gas leaks into basements of homes built over radioactive soil or rock. Energy-efficient buildings, which keep in heated or cooled air, can trap radon indoors and lead to high concentrations of the gas.


Contributor:
Marian R. Chertow, M.P.P.M., Director, Industrial Environmental Management Program, Yale School of Forestry and Environmental Studies.
Source :
World Book 2005