How is SO2 an air pollutant?
Harmful effects of SO2
(i) Sulphur dioxide is an irritating gas to the respiratory tract. At a concentration of even 5 ppm, it causes throat and eye irritation. This results in cough, tears and redness in eyes. It causes breathlessness and affects the voice box also.
(ii) At low concentrations, it is harmful for plants too. It slows down the formation of chlorophyll resulting injured leaves and loss of green colour (chlorosis)
(iii) SO2 reacts with moisture (or rain water) present in air to form sulphurous acid causing acid rain. It damages the marble of buildings and causes diseases in animals, humans and plants,
CaCO3Marble+H2SO4Acid in rain→CaSO4Damaged marble+H2O+CO2