Pollutant: A pollutant is defined as undesirable matter present in excess in the environment.
Atmospheric pollution: It is defined as the effect of undesirable changes occurring in our surroundings which has harmful effects on plants, animals, and human beings.
Air pollution: It is defined as the presence of a contaminant in the atmosphere in a concentration large enough to injure human, plant, and animal life.
Smog: A pollutant that is a combination of oxides of sulfur and nitrogen, partially oxidized hydrocarbons and their derivatives produced by industries and automobiles from a dark, thick dust and soot-laden fog is known as smog.
Photochemical smog: Smog formed by the photochemical reaction in the atmosphere is known as
photochemical smog.