AIR QUALITY INDEX

TAG: GS-3: ENVIRONMENTAL POLLUTION & DEGRADATION

CONTEXT: According to the Central Pollution Control Board (CPCB), the Air Quality Index (AQI) in many areas of Delhi reached the ‘very poor’ category.

EXPLANATION:

About Air Quality Index (AQI):

• 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 widely used National Air Quality Index (NAQI) given by the Central Pollution Control Board is a 24-hour average.
• 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.

What are NAQI standards?

• The mandate provided to the Central Pollution Control Board (CPCB) under the Air (Prevention and Control of Pollution) Act empowers it to set standards for the quality of air.
• Hence the current National Ambient Air Quality Standards were notified in November 2009 by the CPCB.
• Prior to this, India had set Air Quality standards in 1994, and this was later revised in 1998.
• The 2009 standards further lowered the maximum permissible limits for pollutants and made the standards uniform across the nation.
• Earlier, less stringent standards were prescribed for industrial zones as compared to residential areas.

Source:

https://indianexpress.com/article/explained/everyday-explainers/aqi-meaning-delhi-diwali-pm10-9648451/