Human Impact
Pollution is the presence of substances in the air, land, or water that can degrade human health and environmental quality. These substances may come from many sources, but some of the most serious pollution problems are the result of unwanted by-products—commonly called wastes—from human activities.
In the early 1970's, major steps were taken to reduce pollution from human activities, including passage of the Clear Air and Clean Water Acts and establishment of state and federal environmental protection agencies. Many of these efforts were targeted toward large, conspicuous sources of pollution such as factories and municipal sewage systems, and significant progress has been made in reducing pollution from these point sources.
Point source pollution is pollution that comes from a single, identifiable source such as a pipe or smokestack. But many polluting substances do not originate from a single source. Rainwater, for example, may become contaminated as it moves over and through the ground, picking up pollutants from many different sources. This kind of pollution is known as nonpoint source pollution, and now accounts for most of the water pollution in the United States.
Pollutants from nonpoint sources include: fertilizers and pesticides from farms and home landscapes; oil, grease, and toxic fluids from roads, parking areas, leaking underground storage tanks, and improper disposal of used motor vehicle fluids; sediments from poorly managed construction sites, forest lands and stream banks; acid drainage from abandoned mines; and bacteria and nutrients from livestock, pet wastes, and faulty septic tanks. In fact, nonpoint source pollution comes from such a wide variety of human activities that almost everyone contributes to the problem in some way, often without realizing it.
Nonpoint source pollution is a serious problem that costs millions of dollars in lost and damaged resources, degrades environmental quality, and threatens human health. It has been the focus of numerous state, local, and national efforts. The variety of sources and substances that result in nonpoint source pollution often make it difficult to know exactly what actions are needed to reduce or eliminate the problem.
In many cases, the first priorities are to recognize when pollution is taking place, identify the polluting substances, and determine the sources of pollutants. These tasks are part of the mission of National Oceanic and Atmospheric Administration's Center for Coastal Monitoring and Assessment (CCMA). CCMA conducts long-term monitoring of toxic chemicals and environmental conditions at more than 350 sites along the U.S. coasts. Monitoring typically includes measurements of: the concentrations of common pollutants in sediments and the tissues of living organisms; the toxicity of sediments to living organisms; and the abundance and variety of species in bottom communities.
Coastal ecosystems provide communities with food, economic opportunities, recreational resources, and aesthetic enrichment. But despite their importance, these systems are under increasing stress from human activities. More than half of the U.S. population live in coastal areas, and this population continues to grow. Each year, degradation of coastal resources costs millions of dollars. Despite significant progress in reducing pollution from point sources such as discharge from industrial facilities or sewage treatment plants, nearly half of U.S. coastal waters continue to be degraded by rainwater and snowmelt that becomes contaminated as it moves over and through the ground.
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