Context

• The Commission for Air Quality Management (CAQM) has implemented Stage III of the Graded Response Action Plan (GRAP) in the Delhi-NCR region due to worsening air quality.

What is the Graded Response Action Plan?

• The GRAP is a step-by-step plan to counter Delhi-NCR region’s deteriorating air quality.
• It was formulated by the Environmental Pollution Prevention and Control Authority (EPCA) jointly with the Delhi government in 2017. 
• The plan is incremental and adaptable, which means the preventive measures will be updated and escalated according to changes in the AQI.
• Stage 1 of GRAP is activated when the Air Quality Index (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 finally Stage 4 is when it rises to the ‘Severe +’ category (more than 450).

About Commission for Air Quality Management (CAQM)

• The Commission for Air Quality Management (CAQM) was established in 2021 replacing the Environment Pollution (Prevention and Control) Authority.
• The Commission has been implementing the GRAP since 2021.
• While previously, measures were introduced after pollution concentrations reached a certain level, at present, measures are pre-emptively introduced and will kick in based on forecasts in an attempt to prevent the air quality from deteriorating further. 
• For this, the CAQM relies on air quality and meteorological forecasts by the Indian Institute of Tropical Meteorology (IITM) and the India Meteorological Department (IMD).
• The older version of the GRAP was enforced based only on the concentration of PM2.5 and PM10. At present, GRAP is being enforced based on the Air Quality Index (AQI), which takes other pollutants also into account, such as ozone, carbon and oxides of nitrogen.

About Air Quality Index 

• AQI is a number, which is a measure of air quality. The higher the AQI, the worse the air. 
• The colour-coded AQI index was launched in India in 2014, and it 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. 

• There are six categories of AQI, namely ‘Good’ (0-50), ‘Satisfactory’ (51-100), ‘Moderately polluted’ (101-200), ‘Poor’ (201-300), ‘Very Poor’ (301-400), and ‘Severe’ (401-500).
• The pollutants measured include PM 10, PM 2.5, Nitrogen Dioxide, Ozone, Carbon, etc.

What is the impact of these pollutants?

• Among the more harmful pollutants are those of a smaller size, such as particulate matter (PM) 2.5, which is an atmospheric particulate matter of diameter smaller than 2.5 micrometers.
• It causes respiratory problems and reduces visibility. The particles can only be detected with the help of an electron microscope because they are so small.
• Due to their size, the PM 2.5 particles can easily bypass the nose and throat and can easily enter the circulatory system. The particles can also lead to chronic diseases such as asthma, heart attack, bronchitis and other respiratory problems.