Mobile Sources of Air Pollution
“Mobile sources” is a term used to describe a wide variety of vehicles, engines, and equipment that generate air pollution and that move, or can be moved, from place to place:
-“On-road” or highway sources include vehicles used on roads for transportation of passengers or freight. On-road vehicles include light-duty vehicles, light-duty trucks, heavy-duty vehicles, and motorcycles, used for transportation on the road. On-road vehicles may be fueled with gasoline, diesel fuel, or alternative fuels such as alcohol or natural gas.
-“Nonroad” sources include vehicles, engines, and equipment used for construction, agriculture, transportation, recreation, and many other purposes. Within these two broad categories, on-road and nonroad sources are further delineated by size, weight, use, and/or horsepower. Nonroad vehicles, engines and equipment include equipment and vehicles fueled with diesel fuel, gasoline, propane, or natural gas in the following sectors: recreational, construction and mining, industrial, lawn and garden, farm, commercial, logging, airport service, railway maintenance, and recreational marine vessels.
Mobile sources pollute the air through combustion and fuel evaporation. These emissions contribute greatly to air pollution nationwide and are the primary cause of air pollution in many urban areas. Mobile sources contribute four significant air pollutants that affect human health and the environment including Carbon Monoxide, Hydrocarbons, Nitrogen Oxides and Particulate Matter.
Mobile sources also produce several other important air pollutants, such as air toxics and greenhouse gases. Nationwide, mobile sources represent the largest contributor to air toxics. Air toxics are pollutants known or suspected to cause cancer or other serious health or environmental effects. Greenhouse gases, such as carbon dioxide (CO2), trap heat in the Earth’s atmosphere, contributing to global climate change.