AIR QUALITY INDEX(AQI)
WHY IN NEWS ?
- Recently, Delhi experienced its first ‘good’ air quality day of the year on Sunday, boasting an Air Quality Index (AQI) reading of 45, marking the cleanest air quality in the city for the entire year, according to data from the Central Pollution Control Board (CPCB).
WHAT IS AIR QUALITY INDEX(AQI) ?
- AQI measures how safe the air around you is for breathing.
- Organizations that report AQI measure the density of various pollutants in the air (such as PM2.5, PM10, nitrogen dioxide, ozone, etc) at different monitoring stations, in micrograms per cubic metre.
- A particular amount of one pollutant may not be as harmful as the same amount of another pollutant.
- So, each pollutant’s quantity in the air is adjusted to a common scale (say, 0 to 500) that works for all pollutants.
- Finally, the pollutant with the worst sub-index determines the AQI for that time and location.
REAL-TIME AIR QUALITY MEASURE:
- The AQI given by the Ministry of Earth Sciences’ SAFAR unit is real-time, which is commonly cited.
- SAFAR’s AQI is different from the CPCB’s AQI.
- The latter will be markedly lower if there have been phases of better air in the preceding 24 hours.
NATIONAL AIR QUALITY INDEX (NAQI):
- Air Quality Index is a tool for effective communication of air quality status to people in terms, which are easy to understand.
- It transforms complex air quality data of various pollutants into a single number (index value), nomenclature and colour.
- There are six AQI categories, namely Good, Satisfactory, Moderately polluted, Poor, Very Poor, and Severe.
- Each of these categories is decided based on ambient concentration values of air pollutants and their likely health impacts (known as health breakpoints).
- AQ sub-index and health breakpoints are evolved for eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb) for which short-term (upto 24-hours) National Ambient Air Quality Standards are prescribed.
SYLLABUS: PRELIMS, ENVIRONMENT