Air Quality Index (AQI)

About:

• Launched by the central government in 2014 as part of the Swachh Bharat campaign, the AQI was to help simplify the common understanding of pollution.
• The AQI transforms complex air quality data of various pollutants into a single number (index value), nomenclature and colour. The pollutants measured include PM 10, PM 2.5, Nitrogen Dioxide, Ozone, Carbon, etc.
• The colour-coded AQI index helps the public and the government understand the condition of the air and what subsequent measures are to be taken to combat the situation, based on its severity.
• Six categories of AQI:
  • ‘Good’ (0-50)
  • ‘Satisfactory’ (50-100)
  • ‘Moderately polluted’ (100-200)
  • ‘Poor’ (200-300)
  • ‘Very Poor’ (300-400)
  • ‘Severe’ (400-500)
• Calculation of the index:
  • There are six or eight pollutants in the affected air and each of these pollutants is given a weight based on a formula. That weight depends on the kind of impact it has on human health.
  • The worst of these weights is given as composite air quality, so instead of giving six different numbers, and six different colours, it throws up one single colour, one single number to denote the overall impact. Monitoring stations across the country assess these levels.