Pollution is contamination by a chemical or other agent that renders part of the environment unfit for intended or desired use. These uses also and very importantly include all wildlife and ecological requirements to sustain life in all its natural forms.
Pollution damages the Earth's land, water and air. It results in contamination of the earth’s environment with materials that interfere with human health, the quality of life, and the natural functioning of ecosystems (living organisms and their physical surroundings).
Pollution is usually caused by human actions, but can also be the consequence of natural disasters. Pollution can also occur from disruption or damage to wastewater collection and treatment infrastructure due to severe natural events like hurricanes or flooding. Most types of pollution affect the immediate area surrounding the source, and reduce as you move away from the source.
Pollution is often caused by the garbage that people throw on the ground or into oceans, lakes or rivers.
Types of pollution….
There are various types of pollution :
• Air pollution
• Water pollution
• Contaminated land and pollution of groundwater
• Noise pollution
• Light pollution
• Radiation
AIR POLLUTION
I INTRODUCTION
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Air Pollution, addition of harmful substances to the atmosphere resulting in damage to the environment, human health, and quality of life. One of many forms of pollution, air pollution occurs inside homes, schools, and offices; in cities; across continents; and even globally. Air pollution makes people sick—it causes breathing problems and promotes cancer—and it harms plants, animals, and the ecosystems in which they live. Some air pollutants return to Earth in the form of acid rain and snow, which corrode statues and buildings, damage crops and forests, and make lakes and streams unsuitable for fish and other plant and animal life.
Pollution is changing Earth’s atmosphere so that it lets in more harmful radiation from the Sun. At the same time, our polluted atmosphere is becoming a better insulator, preventing heat from escaping back into space and leading to a rise in global average temperatures. Scientists predict that the temperature increase, referred to as global warming, will affect world food supply, alter sea level, make weather more extreme, and increase the spread of tropical diseases.
II MAJOR POLLUTANT SOURCES
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Most air pollution comes from one human activity: burning fossil fuels—natural gas, coal, and oil—to power industrial processes and motor vehicles. Among the harmful chemical compounds this burning puts into the atmosphere are carbon dioxide, carbon monoxide, nitrogen oxides, sulfur dioxide, and tiny solid particles—including lead from gasoline additives—called particulates. Between 1900 and 1970, motor vehicle use rapidly expanded, and emissions of nitrogen oxides, some of the most damaging pollutants in vehicle exhaust, increased 690 percent. When fuels are incompletely burned, various chemicals called volatile organic chemicals (VOCs) also enter the air. Pollutants also come from other sources. For instance, decomposing garbage in landfills and solid waste disposal sites emits methane gas, and many household products give off VOCs.
Some of these pollutants also come from natural sources. For example, forest fires emit particulates and VOCs into the atmosphere. Ultrafine dust particles, dislodged by soil erosion when water and weather loosen layers of soil, increase airborne particulate levels. Volcanoes spew out sulfur dioxide and large amounts of pulverized lava rock known as volcanic ash. A big volcanic eruption can darken the sky over a wide region and affect the Earth’s entire atmosphere. The 1991 eruption of Mount Pinatubo in the Philippines, for example, dumped enough volcanic ash into the upper atmosphere to lower global temperatures for the next two years. Unlike pollutants from human activity, however, naturally occurring pollutants tend to remain in the atmosphere for a short time and do not lead to permanent atmospheric change.
WATER POLLUTION
I INTRODUCTION
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Water Pollution, contamination of rivers, lakes, underground water, bays, or oceans by substances harmful to living things. Water is necessary to life on Earth. All organisms contain it; some live in it; some drink it. Plants and animals require water that is moderately pure, and they cannot survive if their water is loaded with toxic chemicals or harmful microorganisms. If severe, water pollution can kill large numbers of fish, birds, and other animals, in some cases killing all members of a species in an affected area. Pollution makes streams, lakes, and coastal waters unpleasant to look at, to smell, and to swim in. Fish and shellfish harvested from polluted waters may be unsafe to eat. People who ingest polluted water can become ill, and, with prolonged exposure, may develop cancers or bear children with birth defects.
II MAJOR TYPES OF POLLUTANTS
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The major water pollutants are chemical, biological, or physical materials that degrade water quality. Pollutants can be classed into eight categories, each of which presents its own set of hazards.
A Petroleum Products
Oil and chemicals derived from oil are used for fuel, lubrication, plastics manufacturing, and many other purposes. These petroleum products get into water mainly by means of accidental spills from ships, tanker trucks, pipelines, and leaky underground storage tanks. Many petroleum products are poisonous if ingested by animals, and spilled oil damages the feathers of birds or the fur of animals, often causing death. In addition, spilled oil may be contaminated with other harmful substances, such as polychlorinated biphenyls (PCBs).
B Pesticides and Herbicides
Chemicals used to kill unwanted animals and plants, for instance on farms or in suburban yards, may be collected by rainwater runoff and carried into streams, especially if these substances are applied too lavishly. Some of these chemicals are biodegradable and quickly decay into harmless or less harmful forms, while others are nonbiodegradable and remain dangerous for a long time.
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When animals consume plants that have been treated with certain nonbiodegradable chemicals, such as chlordane and dichlorodiphenyltrichloroethane (DDT), these chemicals are absorbed into the tissues or organs of the animals. When other animals feed on these contaminated animals, the chemicals are passed up the food chain. With each step up the food chain, the concentration of the pollutant increases. This process is called biomagnification or bioaccumulation. In one study, DDT levels in ospreys (a family of fish-eating birds) were found to be 10 to 50 times higher than in the fish that they ate, 600 times the level in the plankton that the fish ate, and 10 million times higher than in the water. Animals at the top of food chains may, as a result of these chemical concentrations, suffer cancers, reproductive problems, and death.
Many drinking water supplies, including wells, are contaminated with pesticides from widespread agricultural use. Nitrates, a pollutant often derived from fertilizer runoff, can cause methemoglobinemia in infants, a potentially lethal form of anemia that is also called blue baby syndrome.
SOIL POLLUTION
C Soil Pollution
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.

Noise Pollution
Unwanted sound, or noise, such as that produced by airplanes, traffic, or industrial machinery, is considered a form of pollution. Noise pollution is at its worst in densely populated areas. It can cause hearing loss, stress, high blood pressure, sleep loss, distraction, and lost productivity.
Sounds are produced by objects that vibrate at a rate that the ear can detect. This rate is called frequency and is measured in hertz, or vibrations per second. Most humans can hear sounds between 20 and 20,000 hertz, while dogs can hear high-pitched sounds up to 50,000 hertz. While high-frequency sounds tend to be more hazardous and more annoying to hearing than low-frequency sounds, most noise pollution damage is related to the intensity of the sound, or the amount of energy it has. Measured in decibels, noise intensity can range from zero, the quietest sound the human ear can detect, to over 160 decibels. Conversation takes place at around 40 decibels, a subway train is about 80 decibels, and a rock concert is from 80 to 100 decibels. The intensity of a nearby jet taking off is about 110 decibels. The threshold for pain, tissue damage, and potential hearing loss in humans is 120 decibels. Long-lasting, high-intensity sounds are the most damaging to hearing and produce the most stress in humans.
Solutions to noise pollution include adding insulation and sound-proofing to doors, walls, and ceilings; using ear protection, particularly in industrial working areas; planting vegetation to absorb and screen out noise pollution; and zoning urban areas to maintain a separation between residential areas and zones of excessive noise.
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EFFECTS OF POLLUTION Pollution produces physical and biological effects that vary from mildly irritating to lethal. The more serious of the two are the biological effects. Physical Effects The physical effects of pollution are those that we can see, but they include effects other than actual physical damage. Oil spills. One obvious physical effect of pollution is the result of oil spills that are caused by ship collisions or other accidents. Oil spilled into the seas coats everything it touches. It fouls boat hulls, pier pilings, and shore structures; spoils the beauty of nature by killing fish and birds; and makes beaches unusable. In addition to the physical effects, oil spills require costly cleanup operations. Air pollutants. Air pollutants damage a wide variety of materials. Burning oil and coal produce sulfur oxides, which cause steel to erode two to four times faster than normal. When combined with other pollutants (soot, smoke, lead, asbestos, and so on), sulfur oxide particulates cause corrosion to occur at an even faster rate. By themselves, particulates damage and soil materials, structures, and equipment. Air pollutants speed the erosion of statues and buildings, which in some instances, destroys works of art. Biological Effects The most serious result of pollution is its harmful biological effects on human health and on the food chain of animals, birds, and marine life. Pollution can destroy vegetation that provides food and shelter. It can seriously disrupt the balance of nature, and, in extreme cases, can cause the death of humans. Pesticides, which include herbicides and insecticides, can damage crops; kill vegetation; and poison birds, animals, and fish. Most pesticides are nonselective; they kill or damage life forms other than those intended. For example, pesticides used in an effort to control or destroy undesirable vegetation and insects often destroy birds and small animals. Some life forms develop immunity to pesticides used to destroy them. When that happens, we develop more potent chemicals and the cycle repeats itself. The widespread use of pollutants, such as oil, chemicals, and fertilizers, pollutes our waterways. The biological effect of water pollution is its danger to our water supplies; we require water to survive. Water pollutants are also dangerous to all forms of marine life. Oil is an especially harmful pollutant. It kills surface-swimming animals and sea birds and, once it settles on the bottom, harms shellfish and other types of marine life. The primary pollution concern of Navy personnel involves pollution produced by shipboard wastes. In addition to oil, shipboard wastes include sanitary wastes, galley and laundry waters, chemicals, solid wastes, and combustion by-products of oil- and gasoline-driven engines. Pollutants produced by ships are similar to those generated by municipal and industrial operations. NAVY PROGRAMS FOR POLLUTION CONTROL Based on an Executive Order, all government agencies must provide leadership in the protection and enhancement of the quality of our air and water resources. They also must comply with all environmental laws and regulations. Accordingly, the Secretary of the Navy, the Chief of Naval Operations, and other authorities have issued several pollution control instructions. Those instructions cover the abatement (lowering) of air, water, and noise pollution. In addition, we have a program to preserve our natural, cultural, and historic resources. Clean Air Act Under the Clean Air Act, each state has the primary responsibility for assuring air quality. All naval activities must meet both federal and state standards for preventing air pollution. The Navy has begun taking steps to help meet the nation’s goal of reducing air pollution.
ENVIORMENT
The biophysical environment is the symbiosis between the physical environment and the biological life forms within the environment, and include all variables that comprise the Earth's biosphere. In other contexts environment may also be used to refer to the immediate external surroundings, to a milieu or to the environs within a system or topic, for instance computer science. The biophysical environment can be divided into two categories: the natural environment and the built environment, with some overlap between the two. Following the industrial revolution, the built environment has become an increasingly significant part of the Earth's environment.
The scope of the biophysical environment is all that contained in the biosphere, which is that part of the Earth in which all life occurs. Ecosystems, of which there are numerous types and are a defined part of the biosphere, collectively make up the whole of the biosphere. Within an ecosystem there are habitats in which an organism (including humans) exists. At its most natural, an environment would lack any effects of human activity, although the scale of this activity is such that all areas of the Earth have had at least some influence by humans. At the other end of the scale is the built environment and in some cases it has the biotic component that is virtually absent.
The biophysical environment can vary in scale from microscopic to global in extent. They can also be subdivided according to their attributes. Some examples may be the Marine environment, the atmospheric environment and the terrestrial environment.[1]
STEPS CAN BE TAKEN TO PREVENT AIR POLLUTION BY PEOPLE
On the Road:
• Avoid topping off your gas tank when you fill it.
• Buy radial tires for your car and keep them properly inflated.
• Keep your car well-tuned and support the state's smog-check program.
• Drive Less. Use public transit, carpool, ride a bike, or walk whenever possible. And call-around before you run errands. Does the store really have that thing you need? If you can reduce trips you can save money, time, and cut air pollution.
• When you buy a car, consider purchasing an electric, hybrid, or very-low emission vehicle. Look at the DriveClean website for more details.
At Home
• Conserve Energy -- turn off lights and appliances when you leave the room.
• Check the energy efficiency ratings of refrigerators and other appliances when you buy them. Try to avoid cranking up the air conditioner on a warm day or the heater on a cool day. Look at this website for emission information for thousands of products.
• Use compact fluorescent light bulbs wherever possible in your home. They screw into standard sockets, but use about a quarter of the energy of a standard bulb for the same amount of light. And they last 10 times longer! Ask for them at your hardware or home specialty store.
• Paint with water-based latex paints, not oil-based. It's easier, and much less polluting. Drying paint releases more smog-forming fumes than all the areas' oil refineries and gas stations combined. Buy paint low in Volatile Organic Compounds (VOC's). Close the paint lids tightly when not in use. Use brushes and rollers rather than spray painting, which helps prevent both smog formation and your exposure to air toxics.
• Avoid using lighter fluid to start your barbecue. Cleaner, less-expensive alternatives are available such as metal chimneys using newspaper tinder, or electric probes. Even less polluting are barbecues fired by propane or natural gas.
• Don't use gasoline-powered garden equipment such as lawnmowers or leaf-blowers. Push mowers are best, but electric mowers are much better than mowers that run on gasoline. Use rakes and brooms instead of leaf blowers. Ask your gardener to do the same. That way, you'll reduce both air and noise pollution in your neighborhood.
• Choose professional "wet-cleaning" instead of dry cleaning, and try to buy clothes that don't require dry cleaning. Dry cleaning uses a toxic chemical that is emitted into the air. List of wet cleaners.
• More tips!

In Your Community
• Urge your elected officials to support clean air legislation.
• Support national and state efforts to require better fuel economy and emission standards for all cars, sports utility vehicles (SUVs), and light and heavy-duty trucks, and insist on the continued production and sale of Zero-Emission Vehicles (ZEVs).
• Share these tips with your friends and neighbors and encourage them to help clean the air.
• Join organizations like the Coalition for Clean Air that stand up for your health and safety.
STEPS CAN BE TAKEN BY PEOPLE TO PREVENT WATER POLLUTION
• Toxic products like paints, automobile oil, polishes, and cleaning products should be stored and disposed off properly. As a matter of fact, it is better to use non-toxic, products for the house as far as possible. Also, never dispose off such products by throwing them into your toilet or sink.
• Dispose off your trash in a proper manner and try and incorporate the recycling habit as far as possible. Non-degradable products like tampons, sanitary napkins, and diapers should not be flushed down the toilet, for these can end up damaging the process of sewage treatment, and usually end up as litter on beaches.
• Refrain from throwing litter into streams, lakes, rivers, or seas. If you do spot litter on beaches or in water systems, after ascertaining that it is safe, collect them and dispose off them in any nearby waste disposal system.
• Try using environmentally friendly household products like toiletries, soap-based household cleaning material, and washing powder as far as possible.
• Try using natural fertilizers and pesticides as far as possible, or if not, do not overuse them or over-water gardens and lawns. This will help in reducing the pollutants that get into water systems due to runoffs.
• Automobile oil should be re-used as far as possible. Also, it is important to keep your automobile well maintained in order to prevent leakages of toxic fluids like antifreeze and oil.
• Also, actively conserve water by turning the tap off when you do not need running water, such as while brushing teeth. Apart from preventing water shortages, it lessens the amount of water that needs to be treated.
STEPS TAKEN BY GOVERNMENT TO PREVENT AIR POLLUTION
clean air acts of 1955, 1963, 1970, 1990
In 1955, after many state and local governments had passed legislation dealing with air pollution, the federal government decided that this problem needed to be dealt with on a national level. This was the year Congress passed the Air Pollution Control Act of 1955, the nation's first piece of federal legislation on this issue. The language of the bill identified air pollution as a national problem and announced that research and additional steps to improve the situation needed to be taken. It was an act to make the nation more aware of this environmental hazard.
Eight years later, Congress passed the nation's Clean Air Act of 1963. This act dealt with reducing air pollution by setting emissions standards for stationary sources such as power plants and steel mills. It did not take into account mobile sources of air pollution which had become the largest source of many dangerous pollutants. Once these standards were set, the government also needed to determine deadlines for companies to comply with them. Amendments to the Clean Air Act were passed in 1965, 1966, 1967, and 1969. These amendments authorized the Secretary of Health, Education, and Welfare (HEW) to set standards for auto emissions, expanded local air pollution control programs, established air quality control regions (AQCR), set air quality standards and compliance deadlines for stationary source emissions, and authorized research on low emissions fuels and automobiles.
By 1970, the issue needed to be addressed again. Although important legislative precedents had been set, the existing laws were deemed inadequate. Although technically an amendment, the Clean Air Act of 1970 was a major revision and set much more demanding standards. It established new primary and secondary standards for ambient air quality, set new limits on emissions from stationary and mobile sources to be enforced by both state and federal governments, and increased funds for air pollution research. It was soon discovered that the deadlines set were overly ambitious (especially those for auto emissions). To reach these standards in such a short period of time, the auto industry faced serious economic limitations and seemingly insurmountable technological challenges. Over the next decade, the legislation was once again amended to extend these deadlines and to mandate states to revise their implementation plans. Congress did not amend the Clean Air Act during the decade of the 1980s, in part because President Reagan's administration placed economic goals ahead of environmental goals.
In 1990, after a lengthy period of inactivity, the federal government believed that they should again revise the Clean Air Act due to growing environmental concerns. The Clean Air Act of 1990 addressed five main areas: air-quality standards, motor vehicle emissions and alternative fuels, toxic air pollutants, acid rain, and stratospheric ozone depletion. In many ways, this law set out to strengthen and improve existing regulations.

Air Pollution Control Act of 1955
public law 84-159
"An Act to provide research and technical assistance relating to air pollution control"
This was the first federal legislative attempt to control air pollution at its source. It granted $5 million annually for five years for research by the Public Health Service. The act did little to prevent air pollution, but it made the government aware that this problem existed on the national level. It recognized the dangers facing public health and welfare, agriculture, livestock, and deterioration of property, and reserved for Congress the right to control this growing problem.
amendments of 1960
Extended research funding for four more years.
amendments of 1962
These amendments enforced the principle provisions of the original act. They also called for research to be done by the U.S. Surgeon General to determine the health effects of various motor vehicle exhaust substances.

Clean Air Act of 1963
public law 88-206
"An Act to improve, strengthen, and accelerate programs for the prevention and abatement of air pollution"
This first piece of legislation bearing the name "clean air", in essence, sought to promote public health and welfare. It granted $95 million over a three year period to state and local governments and air pollution control agencies in order to conduct research and create control programs. This act also recognized the dangers of motor vehicle exhaust, and it encouraged the development of emissions standards from these sources as well as from stationary sources. Interstate air pollution from the use of high sulfur coal and oil also needed to be reduced; therefore, this act encouraged the use of technology which removed sulfur from these fuels. To continue action in this area, the Clean Air Act promoted ongoing research, investigations, surveys, and experiments.
amendments of 1965: Motor Vehicle Air Pollution Control Act
These amendments focused on establishing standards for automobile emissions. They also recognized the serious problem of transboundary air pollution and promoted research on its damaging effects on the health and welfare of Canada and Mexico.
amendments of 1966
These amendments, in summary, expanded local air pollution control programs.
amendments of 1967: Air Quality Act
These revolutionary amendments divided parts of the nation into Air Quality Control Regions (AQCRs) as a means of monitoring ambient air. The government also established national emissions standards for stationary sources, which brought about debate because many officials thought it should be dealt with industry by industry, but one national standard was set. These standards established a fixed timetable for state implementation plans (SIPs), and recommended control technologies to achieve the ultimate goals of the SIPs. Again, appropriations were granted to continue research in the area of air pollution control.
amendments of 1969
Extended authorization for research on low emissions fuels and automobiles.

Clean Air Act of 1970
public law 91-604
"An Act to amend the Clean Air Act to provide for a more effective program to improve the quality of the Nation's air."
The amendments in 1970 were an entirely rewritten version of the original Clean Air Act. In principle, it was a law that would show excellent results; however, in the midst of environmental enthusiasm throughout the country, the Clean Air Act proved to be a highly ambitious piece of air pollution abatement legislation. It set National Ambient Air Quality Standards (NAAQS), to protect public health and welfare, and New Source Performance Standards (NSPS), that strictly regulated emissions of a new source entering an area. Standards were also set for hazardous emissions and emissions from motor vehicles. Funds of $30 million went toward research on the growing problem of noise pollution in larger cities. Also, as a new principle, this Clean Air Act allowed citizens the right to take legal action against anyone or any organization, including the government, who is in violation of the emissions standards.
amendments of 1977
The major debate during the creation of these amendments was that of motor vehicle emissions standards. Ultimately, the deadline to meet them, as well as the deadline to meet the ambient air standards, were extended. Also at this time, the government made its first attempt to prevent the destruction of stratospheric ozone. This law also modified the Prevention of Significant Deterioration (PSD) policy designating regions as one of three different classes. By this time the government realized how ambitious the Clean Air Act of 1970 was; therefore, they passed these amendments to set realistic goals.

Clean Air Act of 1990
public law 101-549
"An Act to amend the Clean Air Act to provide for attainment and maintenance of health protective national ambient air quality standards, and for other purposes."
After a decade of virtual dormancy, Congress finally drastically amended the Clean Air Act again to attempt to solve problems of the past as well as deal with new issues. As in the past, the federal government designated states as being responsible for non-attainment areas, but it allowed them to establish deadlines for each source considering the severity of its pollution. It also raised automobile emissions standards and set a definite timetable for reductions in order to tighten control in this area. Through this legislation, the government encouraged the use of low-sulfur fuels as well as alternative fuels as a means of reducing sulfur dioxide in the atmosphere which is a main component of acid precipitation, one of the new problems needing to be dealt with. Also, it mandated the installment of the Best Available Control Technology (BACT) to reduce the amount of air toxics. The government also called for a reduction in the amount of chlorofluorocarbons (CFCs) being used as a way of preventing ozone depletion, a new issue needing to be addressed.

STEPS TAKEN BY GOVERNMENT TO PREVENT WATER POLLUTION
The Clean Water Act is a U.S. federal law that regulates the discharge of pollutants into the nation's surface waters, including lakes, rivers, streams, wetlands, and coastal areas. Passed in 1972 and amended in 1977 and 1987, the Clean Water Act was originally known as the Federal Water Pollution Control Act. The Clean Water Act is administered by the U.S. Environmental Protection Agency (EPA), which sets water quality standards, handles enforcement, and helps state and local governments develop their own pollution control plans.
The original goal of the Clean Water Act was to eliminate the discharge of untreated waste water from municipal and industrial sources and thus make American waterways safe for swimming and fishing (the use of surface water for drinking purposes is covered under separate legislation, the Safe Drinking Water Act). Toward this end, the federal government provided billions of dollars in grants to finance the building of sewage treatment facilities around the country. The Clean Water Act also required businesses to apply for federal permits to discharge pollutants into waterways, as well as to reduce the amount of their discharges over time.
The Clean Water Act has been credited with significantly reducing the amount of pollution that enters the nation's waterways from "point sources," or municipal and industrial discharges. As of 1998, 60 percent of American lakes, rivers, and shoreline were considered clean enough for swimming and fishing. "In the years following passage of the Clean Water Act, the EPA largely succeeded in stemming the 'point source' discharges of big industrial and municipal offenders, whose pipes spewed chemicals directly into oceans, rivers, lakes, and streams," wrote Jeff Glasser and Kenneth T. Walsh in U.S. News and World Report. "It has become clear, however, that 'point source' pollution is only part of the problem."
By the late 1990s, the EPA had changed its focus under the Clean Water Act to emphasize eliminating nonpoint source pollution, like chemicals from agricultural runoff or erosion from logging or construction activities. In a 2000 report to Congress, the EPA cited these diffuse sources of pollution as the top factors making the remaining 40 percent of the nation's waterways too polluted for swimming or fishing. As scientists increasingly recognized the value of wetlands in filtering out pollution, the EPA also began to emphasize wetlands protection under the Clean Water Act. Businesses must be aware of the expanding applications of the Clean Water Act. The law can affect not only discharges of pollution from factory pipes, but also incidental pollution resulting from the activities of smaller enterprises, such as residential development or the construction of a golf course or office building.