The solution of some pollution problems requires cooperation at regional, national, and international levels. For example, some of the acid rain that falls in Canada is caused by smokestacks of coal-burning power plants in the United States. Thus, rejuvenating the lakes of eastern Canada requires the cooperation of electric utilities in Indiana and Ohio. 

In the United States laws have been passed to regulate the discharge of pollutants into the environment. The Environmental Protection Agency (EPA), which was formed through the National Environmental Policy Act (NEPA) of 1969, oversees most federal antipollution activity. The National Environmental Policy Act also mandated the use of environmental impact statements, which require that businesses or governments examine alternatives and acknowledge the possible harmful effects of such activities as opening new factories, building dams, and developing new oil wells. With the advent of massive oil spills from supertankers, the washing up of medical wastes on shores in New York and New Jersey, and an increased buildup of toxic wastes, such international organizations as Greenpeace have become ever more dedicated to preventing environmental abuses and heightening public awareness of environmental issues. (See also Waste, Toxic.) 

The Clean Air Act, the Safe Drinking Water Act, and the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (known as Superfund) are among the laws that set standards for healthy air and water and the safe disposal of toxic chemicals. In 1990 President George Bush signed the Clean Air Act of 1990, the second amending legislation since the original Clean Air Act of 1970. The new law called for reductions in emissions of sulfur dioxide and nitrogen oxide by half, carbon monoxide from vehicles by 70 percent, and other emissions by 20 percent. The number of toxic chemicals monitored by the EPA would increase from 7 to about 250, and industry would be required to control their waste release by means of the best technology available. In the same year, the California Air Resources Board introduced the strictest vehicle-emission controls in the world. By 2003 the hydrocarbon emission of all new cars sold in California would have to be at least 70 percent less than that of 1993 models, and by 1998, 2 percent of all cars (rising to 10 percent by 2003) would have to release no harmful emissions at all. Several Northeastern states followed suit by introducing similar, though slightly less severe, controls. 

This article was contributed by John H. Thomas, professor of biology at Stanford University, and Paul J. Allen, Director of Communications at the Natural Resources Defense Council, Washington, D.C. 

In the United States, the serious campaign against water pollution began in 1972, when Congress passed the Clean Water Act. This law initiated a national goal to end all pollution discharges into surface waters, such as lakes, rivers, streams, wetlands, and coastal waters. The law required those who discharge pollutants into waterways to apply for federal permits and to be responsible for reducing the amount of pollution over time. The law also authorized generous federal grants to help states build water treatment plants that remove pollutants, principally sewage, from wastewater before it is discharged.

Since the passage of the Clean Water Act in 1972, most of the obvious point sources of pollution in the United States have been substantially cleaned up. Municipal sewage plants in many areas are now yielding water so clean that it can be used again. Industries are treating their waste and also changing their manufacturing processes so that less waste is produced. As a result, surface waters are far cleaner than they were in 1972. In 1990 a survey of rivers and streams found that three-quarters of these waters were clean enough for swimming and fishing. Cleaning up the remainder of these rivers and streams will require tackling the more difficult problems of diffuse, nonpoint source pollution.

Congress first took up the nonpoint source problem in 1987, requiring the states to develop programs to combat this kind of pollution. Since interception and treatment of nonpoint pollution is very difficult, the prime strategy is to prevent it.

In urban areas, one obvious sign of the campaign against nonpoint pollution is the presence of stencilled notices often seen beside storm drains: Drains to Bay, Drains to Creek, or Drains To Lake. These signs discourage people from dumping contaminants, such as used engine oil, down grates because the material will likely pollute nearby waterways. Householders are urged to be sparing in their use of garden pesticides and fertilizers in order to reduce contaminated runoff and eutrophication. At construction sites, builders are required to fight soil erosion by laying down tarps, building sediment traps, and seeding grasses.

In the countryside, efforts are underway to reduce pollution from agricultural wastes, fertilizers, and pesticides, and from erosion caused by logging and farming. Farmers and foresters are encouraged to protect streams by leaving streamside trees and vegetation undisturbed; this practice stabilizes banks and traps sediment coming down the slope, preventing sediment build up in water. Hillside fields are commonly ploughed on the contour of the land, rather than up and down the incline, to reduce erosion and to discourage the formation of gullies. Cows are kept away from stream sides and housed in barns where their waste can be gathered and treated. Increasingly, governments are protecting wetlands, which are valuable pollution traps because their plants absorb excess nutrients and their fine sediments absorb other pollutants. In some places, lost wetlands are being restored. Despite these steps, a great deal remains to be done.

In the United States, the EPA is in overall charge of antipollution efforts. The EPA sets standards, approves state control plans, and steps in (if necessary) to enforce its own rules. Under the Safe Drinking Water Act (SDWA), passed in 1974 and amended in 1986 and 1996, the EPA sets standards for drinking water. Among other provisions, the SWDA requires that all water drawn from surface water supplies must be filtered to remove Cryptosporidium bacteria by the year 2000. The law also requires that states map the watersheds from which drinking water comes and identify sources of pollution within those watersheds. While Americas drinking water is among the safest in the world, and has been improving since passage of the SDWA, many water utilities that serve millions of Americans provide tap water that fails to meet the EPA standards.

The EPA has equivalents in many countries, although details of responsibilities vary. For instance, the federal governments may have a larger role in pollution control, as in France, or more of this responsibility may be shifted to the state and provincial governments, as in Canada. Because many rivers, lakes, and ocean shorelines are shared by several nations, many international treaties also address water pollution. For example, the governments of Canada and the United States have negotiated at least nine treaties or agreements, starting with the Canada-U.S. Boundary Waters Treaty of 1909, governing water pollution of the many rivers and lakes that flow along or across their common border.

Several major treaties deal with oceanic pollution, including the 1972 Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter and the 1973 International Convention for the Prevention of Pollution from Ships (known as MARPOL). International controls and enforcement, however, are generally weak.

From the Encarta website