Introduction to Pollution

Pollution, the presence of harmful or irritating substances, called pollutants, in the environment. As the term is generally used, a pollutant is a substance introduced into the environment as a result of human activities. Pollution is especially serious in technologically advanced and heavily populated areas.

Water—in wells, lakes, rivers, and oceans—may be polluted with untreated sewage, garbage, factory wastes, laundry detergents, pesticide residues, and oil spillage. The air of most cities is laden with automobile exhaust, fumes, fuel oil smoke, and chemicals from factories. The land is contaminated with litter, junk, pesticides, and radioactive wastes.

In the last part of the 1960's the public became concerned with the need for preserving or improving the quality of the environment. People became aware that the resources of the earth—land, air, and water—that are needed to sustain life were being threatened by pollution. Scientists warned that the biosphere (the part of the earth that sustains life) can absorb only a limited quantity of pollutants before becoming unfit for living organisms.

Some experts say that to maintain a quality environment it is necessary to limit the growth of the world's population. Others blame pollution not on the growth of population principally but on the economic growth of technologically advanced nations in which the consumption of manufactured products is high.

Although the wastes created by primitive peoples can be objectionable, they do not accumulate because such wastes are reintegrated into nature by the action of microbes and by other natural processes. There is, however, no natural process that can reintegrate into nature the wastes of modern technology, such as discarded automobiles, television sets, plastic bags, and beer cans; and the chemical components of exhaust fumes and most pesticides.

World wide efforts to curb environmental pollution exist, but effective international controls are largely lacking. It is difficult to achieve cooperation for pollution controls with developing countries whose chief concern is to provide basic needs such as food, shelter, and employment for their people. Furthermore, industries in some countries fear that the costs of pollution controls might make it difficult to compete in exporting with rival nations whose pollution controls may be less costly.

Experts agree that effective pollution controls at local, national, and international levels require massive efforts by individual consumers, industry, and government. In the United States, the Environmental Protection Agency was established in 1970 to attack on the federal level the problems of air and water pollution, solid waste management, pesticides, radiation, and noise.


Many types of human industry and activity produce waste products that pollute the air. The major source of air pollution in many parts of the United States and other countries is the exhaust from automobiles and other motor vehicles. In some cities, the exhaust develops into a highly noticeable form of air pollution called smog. Air pollution is believed to contribute significantly to bronchitis, asthma, emphysema, lung cancer, cardiovascular diseases, and allergies. Many kinds of plant damage have also been attributed to air pollution. In addition, there is concern that air pollution—primarily large amounts of carbon dioxide and smoke—may have long-range effects on climate.


Sewage and other objectionable organic matter in water are normally broken down and rendered harmless by beneficial bacteria and other microorganisms living there. When pollutants in enormous amounts are added to a body of water, however, the water's free oxygen supply is depleted, killing off the beneficial organisms. The water is no longer self-cleansing, other forms of life die out, and it eventually becomes biologically dead.

Some pollutants are non-biodegradable—that is, they cannot be broken down by natural biological processes. Examples are certain pesticides, agricultural fertilizers, radioactive material, oil discharges from ships and boats, and various chemicals.

Two types of pollutants fall to earth in a form of precipitation called acid rain. The burning of fossil fuels (coal and oil) by industrial plants releases sulfur dioxide and nitrogen oxide into the air. These oxides then undergo a chemical reaction to become sulfuric acid and nitric acid. These acids are washed out of the air by rain, sleet, or snow and destroy plant and animal life in lakes and ponds. Other pollutants, such as phosphates, provide an excess of plant nutrients, stimulate excessive growth of water plants, and disturb the ecological balance of the waters. Heated water, discharged primarily by the electric power industry, causes thermal pollution. This occurs when water used for industrial cooling is returned to lakes and streams at high temperatures. Not only are most water plants and animals extremely sensitive to even a slight change in temperature, but at high temperatures water cannot hold enough free oxygen.

Efforts to halt water pollution center mainly on the construction of improved sewage treatment plants; the prohibition of the discharge of industrial wastes, municipal wastes, and heated water; and the reduction of the sulfur dioxide content of airborne emissions from industrial plants.

Solid Wastes

With only 5 per cent of the world's population, the United States consumes nearly half of the earth's industrial raw materials. The amount of solid wastes it produces is enormous. Present waste disposal methods pollute land, air, and water. Open dumps take up space and mar the countryside. Incinerators pollute the air; dumping into the sea fouls the waters.

Modern packaging stresses attractiveness, convenience, and durability but tends to squander natural resources and creates mountains of such non-biodegradable waste as metal cans, glass bottles, and plastic containers. To overcome this problem, many communities have established programs to recycle (that is, gather and reuse) glass, paper, plastic, and metal.

Pesticides, Radiation, and Noise

The use of pesticides has increased world food production and has controlled such human diseases as malaria. However, their widespread and often indiscriminate use has not only killed many harmless or beneficial organisms but has also produced a special type of pollution. It is now known that some of the more persistent pesticides, such as DDT, chlordane, and lindane, accumulate in the tissues of birds, fish, other wildlife, and man. These pesticides have caused cancer, fetal damage, and nerve damage in test animals, and pesticide residues are suspected of causing anemia, sterility, cancer, and brain damage in humans.

Radiation occurs naturally but also can be released from certain things that people have produced. Some radiation, for example, has been released from nuclear reactors that generate electricity and process fuels. Testing of nuclear weapons has also released radiation. Another danger lies in possible accidental leakage from stored radioactive wastes. Health hazards from excessive radiation include cancer, eye damage, and damage to reproductive cells.

Noise, especially noise produced by machines, has always been regarded as a nuisance. It has also been known for some time that persons in certain occupations can suffer noise-induced hearing loss. In addition, there is evidence that the population at large can experience some hearing loss because of the amount of noise the environment from human activity. There is also evidence that excessive noise may have psychologically bad effects.