AQI? What is That?...

  Neeraj Kumar |     June 14, 2021

We keep reading or hearing about air pollution and its deadly effect on our health and environment. More recently, we have also been hearing this new abbreviation being mentioned quite regularly: AQI – or Air Quality Index.

As the name suggests, AQI is nothing but a report on the quality of air that we are breathing in a particular place – it informs us and the authorities how polluted the air is, so that a decision can be taken on the measures to control the pollution level.  

In 2014, the Central Pollution Control Board (CPCB) – India’s main pollution control authority – started issuing this ‘report card’ of air quality: it was called the NAQI, or the National Air Quality Index. It aims at providing an easy-to-understand daily report on air quality in specific locations and cities.

The Indian AQI system uses a point scale of 500. The air quality is ranked in this system from ‘Good’ to ‘Severe’. The system follows a ‘One Number-One Colour-One Description’ formula, which makes it easier for us lay people to judge the air quality in the area we live (see The AQI Table). The higher the AQI value, the greater the level of air pollution and the more serious are the health impacts.


The AQI Table

Learn more about the different categories of polluted air and the associated health concerns

Source: CPCB 

The CPCB monitors seven pollutants in our air -- Sulphur Dioxide (SO2), Oxides of Nitrogen (NO2), Respirable Suspended Particulate Matter (RSPM / PM10) Fine Particulate Matter (PM2.5), Ozone, Carbon Dioxide (CO2) and Ammonia (NH3).

How can we check the AQI on a given day of the city or area we live in? We can do it on the CPCB website (, or with the help of applications available on play store such as Safar Air, Air Quality Air Visual, Sameer and AQI India. Many newspapers also carry the daily AQI readings of their cities for the benefit of their readers.

Air pollution is a killer. According to the World Health Organization (WHO), air pollution causes the death of 4.2 million people every year in the world. The 2020 World Air Quality Report says India is the third most polluted country in the world based on the annual average PM2.5 concentration. Twenty-two of the world’s 30 most polluted cities are located in our country.

In cities like Delhi, the main components of air pollution are the PM2.5 and PM10 particles that are present in the air. When the level of these particles rises in the air, they cause difficulty in breathing, irritation in the eyes, etc. 

In the year 2020, many countries – including India – announced very strict lockdowns to control the spread of the coronavirus pandemic. Vehicular traffic became minimal, many industries were shut, and most construction activities were stopped. As a result, clear blue skies reappeared over our heads! Pollution levels went down, and air quality improved dramatically.

However, as soon as lockdowns ended and normal activities resumed, the pollution levels have started rising. What does this tell us? To begin with, it tells us that vehicular movement, dirty fuels, industrial emissions etc are together responsible for air pollution.

Secondly, the clear skies have shown us what is possible and what we can do in future – if we take adequate measures to control emissions, we can bring down air pollution levels in our cities. These measures include introducing better public transport so that more and more people can use that instead of using personal vehicles; introducing cleaner fuels and electric vehicles; controlling emissions from industries; and managing dust emissions in the air.

About the Author

Deputy Programme Manager, Environment and Education Unit, Centre for Science and Environment

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