Air is one of the five basic elements of life system and also an inexhaustible natural resource. It is very essential for the survival of all the living organisms on earth. Air is a mixture of different gases; nitrogen, carbon dioxide, oxygen, argon, trace gases and water vapours. Nitrogen makes up approx 78% of air by volume and Oxygen contributes 21% of earth atmosphere. The presence of water vapour, dust, pollen, pollutants and other particulates vary by region and atmospheric conditions but usually they are present in small amount. The normal composition of total volume of clean air present in atmosphere is as under:
Atmosphere is a dynamic system that continuously receives a wide range of solids, liquids and gasses from both natural and anthropogenic sources. Further, introduction of chemicals, Particulate Matter (PM) or biological materials harmful to human beings or living organisms damage the natural environment and cause pollution. The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing, asthma and worsening of existing respiratory and cardiac conditions. It is a key environmental issue which not only impacts our health but also impacts economy and food security. It is the fifth-leading risk factor for mortality globally (Boogaard et al. 2019). 9 out of 10 people worldwide are exposed to air pollution levels that exceed the World Health Organization's air quality guidelines. (WHO 2021a).