Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials.
Introduction of particulates, biological molecules, or other harmful materials into the Earth's atmosphere
Presence in the atmosphere of large quantities of gases, solids and radiation produced by the burning of natural and artificial fuels, chemical and other industrial processes and nuclear explosions.
The degree to which air is polluted; the type and maximum concentration of man-produced pollutants that should be permitted in the atmosphere.
Any pollutant agent or combination of such agents, including any physical, chemical, biological, radioactive substance or matter which is emitted into or otherwise enters the ambient air and can, in high enough concentrations, harm humans, animals, vegetation or material.