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Pollution is the introduction of contaminants into the natural environment that cause harm. [1] Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants.
Air pollution can cause diseases, allergies, and even death; it can also cause harm to animals and crops and damage the natural environment (for example, climate change, ozone depletion or habitat degradation) or built environment (for example, acid rain). [2] Air pollution can occur naturally or be caused by human activities. [3]
A pollutant or novel entity [1] is a substance or energy introduced into the environment that has undesired effect, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oil) or anthropogenic in origin (i.e. manufactured materials or byproducts).
The international pictogram for environmental hazards.. Environmental hazards are hazards that affect biomes or ecosystems. [1] Well known examples include oil spills, water pollution, slash and burn deforestation, air pollution, ground fissures, [2] and build-up of atmospheric carbon dioxide. [3]
Sources of water pollution are either point sources or non-point sources. [155] Point sources have one identifiable cause, such as a storm drain, a wastewater treatment plant, or an oil spill. Non-point sources are more diffuse. An example is agricultural runoff. [156] Pollution is the result of the cumulative effect over time.
A practical definition of water pollution is: "Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses." [1]: 6 Water is typically referred to as polluted when it is impaired by anthropogenic contaminants.
The U.S. Environmental Protection Agency has categorized 70 different categories of air pollution area source. [1] Locomotives operating on certain linear tracks are examples of a line source, whereas locomotives operating within a railyard are an example of an area source of pollution. Other area sources of air pollution are:
Particulate pollution can occur directly or indirectly from a number of sources including, but not limited to: agriculture, automobiles, construction, forest fires, chemical pollutants, and power plants. [30] Exposure to particulates of any size and composition may occur acutely over a short duration, or chronically over a long duration. [31]