Why in news?

• The air quality in Delhi turned ‘severe’ as its average AQI was 447 on January 14.
• The sudden deterioration in air quality prompted the Commission for Air Quality Management (CAQM) to invoke stage 3 measures under the Graded Response Action Plan (GRAP) across Delhi-NCR with immediate effect.

What’s in today’s article?

• Air Quality Index (AQI)
• Commission for Air Quality Management (CAQM)
• Graded Response Action Plan (GRAP)
• News Summary

Air Quality Index (AQI)

• AQI was launched in October 2014 to disseminate information on air quality in an easily understandable form for the general public.
• The measurement of air quality is based on eight pollutants, namely, PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb
• The AQI transforms complex air quality data of various pollutants into a single number for ease of understanding.
• 

Commission for Air Quality Management (CAQM)?

• CAQM is a statutory body formed under the Commission for Air Quality Management in National Capital Region and Adjoining Areas, Act 2021.
• The commission aims at better coordination, research, identification, and resolution of problems related to air quality in NCR and adjoining areas.

Graded Response Action Plan

• About
  • GRAP is a set of emergency measures that kick in to prevent further deterioration of air quality once it reaches a certain threshold in the Delhi-NCR region.
  • It was approved by the Supreme Court in 2016 and notified in 2017.
    • The plan was formulated after several meetings between Environment Pollution (Prevention and Control) Authority (EPCA), state government and experts.
  • GRAP works only as an emergency measure.
  • The plan does not include action by various state governments to be taken throughout the year to tackle industrial, vehicular and combustion emissions.
• Nature
  • 
  • GRAP is incremental in nature and thus, when the air quality dips from ‘poor’ to ‘very poor,’ measures listed under both sections have to be followed.
  • Stage 1 of GRAP is activated when the AQI is in the ‘poor’ category (201 to 300);
  • Stage 2 is when it’s in the ‘Very poor’ category (301-400);
  • Stage 3 is when the AQI is the ‘Severe’ category (401-450); and
  • Stage 4 is when it rises to the ‘Severe +’ category (more than 450).

News Summary: Delhi AQI severe

• Delhi’s 24-hour average air quality index (AQI) was recorded at 447 (severe) on January 14. As a result, CAQM invoked stage 3 measures under the GRAP across Delhi-NCR.
• The sudden to a spike in pollution levels was due to the combination of:
  • low wind speed,
  • frigid temperatures,
  • rise in the moisture levels,
  • low mixing heights and
  • impact of biomass combustion across the city
• Invoked for the third time this winter season, the eight measures include a ban on BS- III petrol and BS-IV diesel four-wheelers plying across Delhi-NCR region.
• The measures also effectively ban private construction in the region.