We can survive for some time without food, but we cannot survive even for a few minutes without air. This simple fact tells us how important clean air is to us. One of your observations in the above activity could be the differences in the amount of smoke in the atmosphere. Do you know where the smoke could have come from? Addition of such substances to the atmosphere modifies it. When air is contaminated by unwanted substances which have a harmful effect on both the living and the non-living, it is referred to as air pollution.

WHAT IS AIR POLLUTION??

Air is composed of ~78% nitrogen, ~21% oxygen, ~0.9% argon. The remaining elements include carbon dioxide, water vapour, hydrogen, and other trace elements. Although gases like carbon dioxide and methane may only exist in small absolute concentrations, their outsized heat-trapping potential as greenhouse gases makes them the major factor in accelerating climate change. Air pollution occurs when there is an alteration to the composition of air, either by volume, or in the chemical, physical, or biological properties. The atmosphere is a delicate balance of elements and particles. Any imbalance, even in small proportions can be detrimental to living organisms including animals and crops. Air pollution is caused by a combination of gaseous and particulate pollutants such as carbon dioxide, methane, and nitrogen dioxide emitted from point sources such as factories and motor vehicles that burn fuel. Some gaseous emissions are visible to the eye and sometimes may even diffuse into the atmosphere and become invisible. Particulate pollution, on the other hand, such as soot and black carbon, is always visible.

HOW DOES AIR GET POLLUTED?

The substances which contaminate the air are called air pollutants. Sometimes, such substances may come from natural sources like smoke and dust arising from forest fires or volcanic eruptions. Pollutants are also added to the atmosphere by certain human activities. The sources of air pollutants are factories , power plants, automobile exhausts and burning of firewood and dung cakes. Many respiratory problems are caused by air pollution. Let us now try to find out the substances or pollutants which are present in the polluted air. Have you noticed how rapidly the number of vehicles is increasing in our cities? Vehicles produce high levels of pollutants like carbon monoxide, carbon dioxide, nitrogen oxides and smoke . Carbon monoxide is produced from incomplete burning of fuels such as petrol and diesel. It is a poisonous gas. It reduces the oxygen-carrying capacity of the blood.