Anything additional gas, particles or odours that are introduced into the air (either by nature or human activity) to destroy this natural balance can be called air pollution.
Air pollution for children
Things that pollute the air are called pollutants. Examples of pollutants include nitrogen oxides, carbon monoxides, hydrocarbons, sulphur oxides (usually from factories), sand or dust particles, and organic compounds that can evaporate and enter the atmosphere.