Dear student,
Air pollutant can be defined as the substance which effect the human health and alters the composition of environment. There are mainly oxides of S, N and C which act as air pollutant.
The oxides of N and C are mainly added though automobiles whereas oxides of S are mainly added through industrial smoke. Some common oxides of S are SO2, SO3 etc.
SO2 that is named as sulfur dioxide is also a pollutant as it can react easily with water to form sulfuric acid (H2SO4) which causes acidic nature of rain water. Hence it also act as air pollutant as it has nasty, sharp smell ans easily react with other compounds to form the harmful compounds.
Regards