What is Air Quality Index? What does it tell about the condition of air?

Air Quality Index, or AQI for short, gives us a rough idea about how good or bad the quality of air in a particular area is. A high AQI value means a higher level of air pollution. India introduced its own AQI system in 2015 to keep a tab on its rising pollution. Before that, we were relying on the US Air Quality Index, which didn’t fit the bill, given the different conditions and pollutants found here.

India has been measuring pollutants in the air for decades now. It started making them public recently. On a table of 1 t0 500, the pollution table is divided into six coloured bands. It begins with the good green band, in which the AQI level is set between 1 and 50. The worst is the red band where the AQI level is fixed at 401 to 500.      
 
After Diwali, the AQI level at several spots in Delhi had reached 500, which has been categorised as severe, prompting the government to take some strict measures
 
The Environmental Protection Agency (EPA) calculates the AQI for all the major air pollutants. These are ground-level ozone, particle pollution or particulate matter -- that is PM2.5 and pm 10 -- besides Carbon monoxide, Sulfur dioxide and Nitrogen dioxide.
 
The Indian AQI was tailor-made for our needs, as it also measured lead and ammonia -- which the US AQI did not. It also gives real-time data on air quality. Each of these pollutants has been given a weight according to its impact on human health. The AQI is a composite score of all the major pollutants present in the air. 
 
The northern states, including Delhi, have seen a rise in AQI levels over the past decade due to a rise in population, which led to a sharp jump in the number of vehicles to transport them and also the goods they consume. The recent rise in slash and burn farming has also contributed to the air pollution, which turns deadly in the capital during winters every year.

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