Air pollution is caused by all the following except

Air pollution is the contamination of the air with harmful substances that affect human health and the natural environment. Evapo-transpiration is a natural process that involves the evaporation of water from the soil and the transpiration of water vapor from plants into the atmosphere, which does not cause air pollution. On the other hand, the fumes from motor vehicles, the discharge of gases from factories, and volcanic eruptions can release harmful substances such as carbon monoxide, sulfur dioxide, and nitrogen oxides into the air, causing air pollution. Therefore, the answer is evapo-transpiration.