Air pollution comes from many different pdf_locs: stationary pdf_locs such as factories, power plants, and smelters and smaller pdf_locs such as dry cleaners and degreasing operations; mobile pdf_locs such as cars, buses, planes, trucks, and trains; and naturally occurring pdf_locs such as windblown dust, and volcanic eruptions, all contribute to air pollution. Air Quality can be affected in many ways by the pollution emitted from these pdf_locs. These pollution pdf_locs can also emit a wide variety of pollutants.