More recently research has revealed that many chemical pollutants, such as EDT and Pubs mimic sex hormones and interfere with the human body’s reproductive and developmental functions. These substances are known as endocrine disrupter. 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 peculate 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 plopped 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. 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. Nippon-source pollution comes from dispersed or uncontaminated 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. EDT, a nondurable 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 nondurable chemical compounds. I A. I Air Pollution I Brown Smog Over Phoenix, Arizona I Smog is caused by industrial and automobile pollution. It is compounded by imperative 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.
Incarnate Encyclopedia Eric Camp/Photostat NYC Human contamination of Earth’s atmosphere can take many forms and has existed since 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 ported of London in his treatise Fumigants, the weary Traveler, at many Miles distance, sooner smells, than sees the City to which he repairs.
This is that pernicious Smoke which fullness all her Glory, superconducting a soot Crust or Fur 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 lobular 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 C. S. Steel-mill town of Donors, Pennsylvania. In 1 952, about 4,000 Londoner died of its effects. A second type of smog, photochemical smog, began reducing air quality over large cities like Los Angels in the sass. 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. I Smog over Santiago I 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 1 993 the Chilean government has been working with an agency in the United States to improve air quality in Santiago. I Incarnate Encyclopedia I Robert Fierce/Woodwind 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 offish 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 roundhouse 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 1 25,000 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 (CIFS) (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.
I B. Water Pollution Major Oil Spills Throughout the World I The demand for fresh water rises continuously as the world’s population rows. 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.
I Polluted River in the united Kingdom I I 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 Nippon pollution. Point pollution involves those pollution sources from which distinct chemicals can be identified, such as factories, refineries or outfall pipes.
Nippon 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. I Incarnate Encyclopedia I 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 (ERA) 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. I Industrial Water pollution I I Industrial Water Pollution I Industrial pollutants that run into streams, rivers, or lakes can have serious 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. I Incarnate Encyclopedia I Sigma/Corgis I Water runoff, a Nippon 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 transportation, 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 Pastries pesticide, 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 1 9905. 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 overfeeding.