Pollution, contamination of Earth’s environment with materials that interfere with human health, the quality of life, or the natural functioning of ecosystems (living organisms and their physical surroundings). Although some environmental pollution is a result of natural causes such as volcanic eruptions, most is caused by human activities. Sidebars| SIDEBAR | Climate Change 2001:The Scientific Basis| The Intergovernmental Panel on Climate Change (IPCC) is an international group of scientists that evaluates scientific and technical information related to climate change and global warming (an increase in Earth’s surface temperature).
The IPCC publishes an assessment of the latest scientific data related to climate change about every five years. In its Third Assessment Report, released in January 2001 and summarized here, the IPCC sharply increased its projections, predicting a global average surface temperature rise of 1. 4 to 5. 8°C (2. 5 to 10. 4°F) over the period 1990 to 2100 compared to a previous assessment of 1. 0 to 3. 5°C (1. 8 to 6. 3°F) for the same period. This IPCC report also for the first time identified human activity as the primary cause for global warming. | open sidebar| There are two main categories of polluting materials, or pollutants.
Biodegradable pollutants are materials, such as sewage, that rapidly decompose by natural processes. These pollutants become a problem when added to the environment faster than they can decompose (see Sewage Disposal). Nondegradable pollutants are materials that either do not decompose or decompose slowly in the natural environment. Once contamination occurs, it is difficult or impossible to remove these pollutants from the environment. Sidebars| HISTORICAL ESSAYS | Health-Care Systems in Post-Colonial Africa| Encarta Historical Essays reflect the knowledge and insight of leading historians.
This collection of essays is assembled to support the National Standards for World History. In this essay, Oliver Osborne of the University of Washington argues that post-colonial rule and turmoil in Africa has not diminished the continent’s diverse health care systems but rather demanded collaboration among them. | open sidebar| Nondegradable compounds such as dichlorodiphenyltrichloroethane (DDT), dioxins, polychlorinated biphenyls (PCBs), and radioactive materials can reach dangerous levels of accumulation as they are passed up the food chain into the bodies of progressively larger animals.
For example, molecules of toxic compounds may collect on the surface of aquatic plants without doing much damage to the plants. A small fish that grazes on these plants accumulates a high concentration of the toxin. Larger fish or other carnivores that eat the small fish will accumulate even greater, and possibly life-threatening, concentrations of the compound. This process is known as bioaccumulation. | | II. | IMPACTS OF POLLUTION| Sidebars| HISTORIC HEADLINES | Minamata Disease Victims| In the 1950s, residents of Minamata, Japan, began experiencing unusual symptoms, including numbness, vision problems, and convulsions.
Several hundred people died. The cause was discovered to be mercury ingestion: A local industry had dumped the toxic chemical into Minamata Bay, poisoning fish and thousands of people. In 1997, after a massive cleanup, Japan announced that the bay had been cleared of the contaminant. | open sidebar| Because humans are at the top of the food chain, they are particularly vulnerable to the effects of nondegradable pollutants. This was clearly illustrated in the 1950s and 1960s when residents living near Minamata Bay, Japan, developed nervous disorders, tremors, and paralysis in a mysterious epidemic.
More than 400 people died before authorities discovered that a local industry had released mercury into Minamata Bay. This highly toxic element accumulated in the bodies of local fish and eventually in the bodies of people who consumed the fish. More recently research has revealed that many chemical pollutants, such as DDT and PCBs, mimic sex hormones and interfere with the human body’s reproductive and developmental functions. These substances are known as endocrine disrupters. See Occupational and Environmental Diseases. Pollution also has a dramatic effect on natural resources.
Ecosystems such as forests, wetlands, coral reefs, and rivers perform many important services for Earth’s environment. They enhance water and air quality, provide habitat for plants and animals, and provide food and medicines. Any or all of these ecosystem functions may be impaired or destroyed by pollution. Moreover, because of the complex relationships among the many types of organisms and ecosystems, environmental contamination may have far-reaching consequences that are not immediately obvious or that are difficult to predict.
For instance, scientists can only speculate on some of the potential impacts of the depletion of the ozone layer, the protective layer in the atmosphere that shields Earth from the Sun’s harmful ultraviolet rays. Another major effect of pollution is the tremendous cost of pollution cleanup and prevention. The global effort to control emissions of carbon dioxide, a gas produced from the combustion of fossil fuels such as coal or oil, or of other organic materials like wood, is one such example.
The cost of maintaining annual national carbon dioxide emissions at 1990 levels is estimated to be 2 percent of the gross domestic product for developed countries. In addition to its effects on the economy, health, and natural resources, pollution has social implications. Research has shown that low-income populations and minorities do not receive the same protection from environmental contamination as do higher-income communities. Toxic waste incinerators, chemical plants, and solid waste dumps are often located in low-income communities because of a lack of organized, informed community involvement in municipal decision-making processes. | III. | TYPES OF POLLUTION| Pollution exists in many forms and affects many different aspects of Earth’s environment. Point-source pollution comes from specific, localized, and identifiable sources, such as sewage pipelines or industrial smokestacks. Nonpoint-source pollution comes from dispersed or uncontained sources, such as contaminated water runoff from urban areas or automobile emissions. The effects of these pollutants may be immediate or delayed. Primary effects of pollution occur immediately after contamination occurs, such as the death of marine plants and wildlife after an oil spill at sea.
Secondary effects may be delayed or may persist in the environment into the future, perhaps going unnoticed for many years. DDT, a nondegradable compound, seldom poisons birds immediately, but gradually accumulates in their bodies. Birds with high concentrations of this pesticide lay thin-shelled eggs that fail to hatch or produce deformed offspring. These secondary effects, publicized by Rachel Carson in her 1962 book, Silent Spring, threatened the survival of species such as the bald eagle and peregrine falcon, and aroused public concern over the hidden effects of nondegradable chemical compounds. | A. | Air Pollution| | | | | Brown Smog Over Phoenix, Arizona| | | | | | | | | | | | | | | | | Brown Smog Over Phoenix, Arizona| Smog is caused by industrial and automobile pollution. It is compounded by temperature inversions, which cause the air pollution to be kept in a particular area for extended periods. Continued exposure to smog can result in respiratory problems, eye irritation, and even death. | Encarta Encyclopedia| Eric Kamp/Phototake NYC| | | | | | | | | | | | | | | | | Human contamination of Earth’s atmosphere can take many forms and has existed ince humans first began to use fire for agriculture, heating, and cooking. During the Industrial Revolution of the 18th and 19th centuries, however, air pollution became a major problem. As early as 1661 British author and founding member of the British Royal Society John Evelyn reported of London in his treatise Fumifugium, “… the weary Traveller, at many Miles distance, sooner smells, than sees the City to which he repairs. This is that pernicious Smoake which fullyes all her Glory, superinducing a sooty Crust or Furr upon all that it lights. ” Urban air pollution is commonly known as smog. The dark London smog that Evelyn wrote of is generally a smoky mixture of carbon monoxide and organic compounds from incomplete combustion (burning) of fossil fuels such as coal, and sulfur dioxide from impurities in the fuels. As the smog ages and reacts with oxygen, organic and sulfuric acids condense as droplets, increasing the haze. Smog developed into a major health hazard by the 20th century. In 1948, 19 people died and thousands were sickened by smog in the small U.
S. steel-mill town of Donora, Pennsylvania. In 1952, about 4,000 Londoners died of its effects. A second type of smog, photochemical smog, began reducing air quality over large cities like Los Angeles in the 1930s. This smog is caused by combustion in car, truck, and airplane engines, which produce nitrogen oxides and release hydrocarbons from unburned fuels. Sunlight causes the nitrogen oxides and hydrocarbons to combine and turn oxygen into ozone, a chemical agent that attacks rubber, injures plants, and irritates lungs.
The hydrocarbons are oxidized into materials that condense and form a visible, pungent haze. | | | | Smog over Santiago| | | | | | | | | | | | | | | | | Smog over Santiago| Set in an enclosed valley between the coastal range and the Andes Mountains, Santiago, Chile, experiences high levels of air pollution. Vehicular and industrial emissions, street dust, thermal inversions and the city’s location all contribute to the problem. Since 1993 the Chilean government has been working with an agency in the United States to improve air quality in Santiago. Encarta Encyclopedia| Robert Frerck/Woodfin Camp and Associates, Inc. | | | | | | | | | | | | | | | | | Eventually most pollutants are washed out of the air by rain, snow, fog, or mist, but only after traveling large distances, sometimes across continents. As pollutants build up in the atmosphere, sulfur and nitrogen oxides are converted into acids that mix with rain. This acid rain falls in lakes and on forests, where it can lead to the death of fish and plants, and damage entire ecosystems. Eventually the contaminated lakes and forests may become lifeless.
Regions that are downwind of heavily industrialized areas, such as Europe and the eastern United States and Canada, are the hardest hit by acid rain. Acid rain can also affect human health and man-made objects; it is slowly dissolving historic stone statues and building facades in London, Athens, and Rome. One of the greatest challenges caused by air pollution is global warming, an increase in Earth’s temperature due to the buildup of certain atmospheric gases such as carbon dioxide. With the heavy use of fossil fuels in the 20th century, atmospheric concentrations of carbon dioxide have risen dramatically.
Carbon dioxide and other gases, known as greenhouse gases, reduce the escape of heat from the planet without blocking radiation coming from the Sun. Because of this greenhouse effect, average global temperatures are expected to rise 1. 4 to 5. 8 Celsius degrees (2. 5 to 10. 4 Fahrenheit degrees) by the year 2100. Although this trend appears to be a small change, the increase would make the Earth warmer than it has been in the last 125,000 years, possibly changing climate patterns, affecting crop production, disrupting wildlife distributions, and raising the sea level.
Air pollution can also damage the upper atmospheric region known as the stratosphere. Excessive production of chlorine-containing compounds such as chlorofluorocarbons (CFCs) (compounds formerly used in refrigerators, air conditioners, and in the manufacture of polystyrene products) has depleted the stratospheric ozone layer, creating a hole above Antarctica that lasts for several weeks each year. As a result, exposure to the Sun’s harmful rays has damaged aquatic and terrestrial wildlife and threatens human health in high-latitude regions of the northern and southern hemispheres. | B. | Water Pollution| | | | | Major Oil Spills Throughout the World| | | | | The demand for fresh water rises continuously as the world’s population grows. From 1940 to 1990 withdrawals of fresh water from rivers, lakes, reservoirs, and other sources increased fourfold. Of the water consumed in the United States in 1995, 39 percent was used for irrigation, 39 percent was used for electric power generation, and 12 percent was used for other utilities; industry and mining used 7 percent, and the rest was used for agricultural livestock and commercial purposes. | | | Polluted River in the United Kingdom| | | | | | | | | | | | | | | | | Polluted River in the United Kingdom| The pollution of rivers and streams with chemical contaminants has become one of the most critical environmental problems of the 20th century. Waterborne chemical pollution entering rivers and streams comes from two major sources: point pollution and nonpoint pollution. Point pollution involves those pollution sources from which distinct chemicals can be identified, such as factories, refineries or outfall pipes.
Nonpoint pollution involves pollution from sources that cannot be precisely identified, such as runoff from agricultural or mining operations or seepage from septic tanks or sewage drain fields. It is estimated that each year 10 million people die worldwide from drinking contaminated water. | Encarta Encyclopedia| Ben Osborne/Oxford Scientific Films| | | | | | | | | | | | | | | | | Sewage, industrial wastes, and agricultural chemicals such as fertilizers and pesticides are the main causes of water pollution. The U. S.
Environmental Protection Agency (EPA) reports that about 37 percent of the country’s lakes and estuaries, and 36 percent of its rivers, are too polluted for basic uses such as fishing or swimming during all or part of the year. In developing nations, more than 95 percent of urban sewage is discharged untreated into rivers and bays, creating a major human health hazard. | | | | Industrial Water Pollution| | | | | | | | | | | | | | | | | Industrial Water Pollution| Industrial pollutants that run into streams, rivers, or lakes can have erious effects on wildlife, plants, and humans. In the United States there are strict rules for the amount and composition of substances that factories can release into bodies of water. These rules are not always enforced, and much industrial water pollution comes from accidental chemical or oil spills. | Encarta Encyclopedia| Sygma/Corbis| | | | | | | | | | | | | | | | | Water runoff, a nonpoint source of pollution, carries fertilizing chemicals such as phosphates and nitrates from agricultural fields and yards into lakes, streams, and rivers.
These combine with the phosphates and nitrates from sewage to speed the growth of algae, a type of plantlike organism. The water body may then become choked with decaying algae, which severely depletes the oxygen supply. This process, called eutrophication, can cause the death of fish and other aquatic life. Agricultural runoff may be to blame for the growth of a toxic form of algae called Pfiesteria piscicida, which was responsible for killing large amounts of fish in bodies of water from the Delaware Bay to the Gulf of Mexico in the late 1990s.
Runoff also carries toxic pesticides and urban and industrial wastes into lakes and streams. Erosion, the wearing away of topsoil by wind and rain, also contributes to water pollution. Soil and silt (a fine sediment) washed from logged hillsides, plowed fields, or construction sites, can clog waterways and kill aquatic vegetation. Even small amounts of silt can eliminate desirable fish species. For example, when logging removes the protective plant cover from hillsides, rain may wash soil and silt into streams, covering the gravel beds that trout or salmon use for spawning.
The marine fisheries supported by ocean ecosystems are an essential source of protein, particularly for people in developing countries. Yet pollution in coastal bays, estuaries, and wetlands threatens fish stocks already depleted by overfishing. In 1989, 260,000 barrels of oil spilled from the oil tanker Exxon Valdez into Alaska’s Prince William Sound, a pristine and rich fishing ground. In 1999 there were 8,539 reported spills in and around U. S. waters, involving 4. 4 billion liters (1. 2 billion gallons) of oil. | | C. | Soil Pollution| | | | | Pest Control or Pollution? | | | | | | | | | | | | | | | | Pest Control or Pollution? | Pest control has become a difficult issue for farmers because of its potential environmental impact. Although the insecticide being sprayed on this potato field will eliminate a generation of Colorado potato beetles, it may also contaminate local food and water sources. | Encarta Encyclopedia| Blair Seitz/Photo Researchers, Inc. | | | | | | | | | | | | | | | | | Soil is a mixture of mineral, plant, and animal materials that forms during a long process that may take thousands of years. It is necessary for most plant growth and is essential for all agricultural production.
Soil pollution is a buildup of toxic chemical compounds, salts, pathogens (disease-causing organisms), or radioactive materials that can affect plant and animal life. Unhealthy soil management methods have seriously degraded soil quality, caused soil pollution, and enhanced erosion. Treating the soil with chemical fertilizers, pesticides, and fungicides interferes with the natural processes occurring within the soil and destroys useful organisms such as bacteria, fungi, and other microorganisms. For instance, strawberry farmers in California fumigate the soil with methyl bromide to destroy organisms that may harm young strawberry plants.
This process indiscriminately kills even beneficial microorganisms and leaves the soil sterile and dependent upon fertilizer to support plant growth. This results in heavy fertilizer use and increases polluted runoff into lakes and streams. Improper irrigation practices in areas with poorly drained soil may result in salt deposits that inhibit plant growth and may lead to crop failure. In 2000 bc, the ancient Sumerian cities of the southern Tigris-Euphrates Valley in Mesopotamia depended on thriving agriculture. By 1500 bc, these cities had collapsed largely because of crop failure due to high soil salinity.
The same soil pollution problem exists today in the Indus Valley in Pakistan, the Nile Valley in Egypt, and the Imperial Valley in California. | | D. | Solid Waste| | | | | Components of Municipal Solid Waste| | | | | | | | | | | | | | | | | Components of Municipal Solid Waste| A person living in an industrialized nation produces a great variety of solid waste, often a mix of potentially reusable or recyclable items (such as paper and yard waste) and largely nonrecyclable material (such as food waste and many types of plastic).
Of the municipal solid waste (the waste collected from residences and businesses) produced in the United States in 2000, about two-fifths of the paper, metal, and yard waste was recycled, and about one-quarter of the glass was recycled. | Encarta Encyclopedia| © Microsoft Corporation. All Rights Reserved. | | | | | | | | | | | | | | | | | Solid wastes are unwanted solid materials such as garbage, paper, plastics and other synthetic materials, metals, and wood. Billions of tons of solid waste are thrown out annually.
The United States alone produces about 200 million metric tons of municipal solid waste each year (see Solid Waste Disposal). A typical American generates an average of 2 kg (4 lb) of solid waste each day. Cities in economically developed countries produce far more solid waste per capita than those in developing countries. Moreover, waste from developed countries typically contains a high percentage of synthetic materials that take longer to decompose than the primarily biodegradable waste materials of developing countries. | | | | Overflowing Landfill| | | | | | | | | | | | | | | | Overflowing Landfill| An average city dweller may produce a ton of refuse in a year, a volume that rapidly overflows local dumps. Cities running out of space for landfill often turn to incinerating their waste or transporting it to other areas, although up to 90 percent of the material might have been recycled. | Encarta Encyclopedia| Rafael Macia/Photo Researchers, Inc. | | | | | | | | | | | | | | | | | Areas where wastes are buried, called landfills, are the cheapest and most common disposal method for solid wastes worldwide.
But landfills quickly become overfilled and may contaminate air, soil, and water. Incineration, or burning, of waste reduces the volume of solid waste but produces dense ashen wastes (some of which become airborne) that often contain dangerous concentrations of hazardous materials such as heavy metals and toxic compounds. Composting, using natural biological processes to speed the decomposition of organic wastes, is an effective strategy for dealing with organic garbage and produces a material that can be used as a natural fertilizer.
Recycling, extracting and reusing certain waste materials, has become an important part of municipal solid waste strategies in developed countries. According to the EPA, more than one-fourth of the municipal solid waste produced in the United States is now recycled or composted. Recycling also plays a significant, informal role in solid waste management for many Asian countries, such as India, where organized waste-pickers comb streets and dumps for items such as plastics, which they use or resell.
Expanding recycling programs worldwide can help reduce solid waste pollution, but the key to solving severe solid waste problems lies in reducing the amount of waste generated. Waste prevention, or source reduction, such as altering the way products are designed or manufactured to make them easier to reuse, reduces the high costs associated with environmental pollution. | | E. | Hazardous Waste| | | | | Toxic Waste in Love Canal| | | | | | | | | | | | | | | | | Toxic Waste in Love Canal|
Residents of the Love Canal area in Niagara Falls were forced to evacuate when hazardous wastes leaking from a former disposal site threatened their health and homes in the late 1970s. One of the most notorious cases of toxic waste leakage, the crisis received attention on both local and national levels. Investigation spurred by public outrage revealed that many waste disposal sites like Love Canal existed nationwide; New York alone had several hundred. Several states passed stricter regulations on industrial waste disposal and allocated billions of dollars for the cleanup of contaminated areas. Encarta Encyclopedia| Jan Callagan/Phototake NYC| | | | | | | | | | | | | | | | | Hazardous wastes are solid, liquid, or gas wastes that may be deadly or harmful to people or the environment and tend to be persistent or nondegradable in nature. Such wastes include toxic chemicals and flammable or radioactive substances, including industrial wastes from chemical plants or nuclear reactors, agricultural wastes such as pesticides and fertilizers, medical wastes, and household hazardous wastes such as toxic paints and solvents.
About 400 million metric tons of hazardous wastes are generated each year. The United States alone produces about 250 million metric tons—70 percent from the chemical industry. The use, storage, transportation, and disposal of these substances pose serious environmental and health risks. Even brief exposure to some of these materials can cause cancer, birth defects, nervous system disorders, and death. Large-scale releases of hazardous materials may cause thousands of deaths and contaminate air, water, and soil for many years.
The world’s worst nuclear reactor accident took place near Chernobyl’, Ukraine, in 1986 (see Chernobyl’ Accident). The accident killed at least 31 people, forced the evacuation and relocation of more than 200,000 more, and sent a plume of radioactive material into the atmosphere that contaminated areas as far away as Norway and the United Kingdom. Until the Minamata Bay contamination was discovered in Japan in the 1960s and 1970s, most hazardous wastes were legally dumped in solid waste landfills, buried, or dumped into lakes, rivers, and oceans.
Legal regulations now restrict how such materials may be used or disposed, but such laws are difficult to enforce and often contested by industry. It is not uncommon for industrial firms in developed countries to pay poorer countries to accept shipments of solid and hazardous wastes, a practice that has become known as the waste trade. Moreover, cleaning up the careless dumping of the mid-20th century is costing billions of dollars and progressing very slowly, if at all. The United States has an estimated 217,000 hazardous waste dumps that need immediate action.
Cleaning them up could take more than 30 years and cost $187 billion. Hazardous wastes of particular concern are the radioactive wastes from the nuclear power and weapons industries. To date there is no safe method for permanent disposal of old fuel elements from nuclear reactors. Most are kept in storage facilities at the original reactor sites where they were generated. With the end of the Cold War, nuclear warheads that are decommissioned, or no longer in use, also pose storage and disposal problems. | | F. | Noise Pollution| Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.