Current Context : The Supreme Court questioned the Delhi government, over the “delay” in implementing stage IV of the Graded Response Action Plan (GRAP).

About Stage IV of the Graded Response Action Plan (GRAP)

What is Stage IV of GRAP?

1. Stage IV represents the most stringent level of the Graded Response Action Plan, invoked when the Air Quality Index (AQI) exceeds 450, reaching the “Severe+” category. It is designed to prevent further air quality deterioration in Delhi-NCR.

Major Restrictions Under Stage IV:

1. Ban on Construction and Demolition (C&D) Activities:All non-essential C&D activities are prohibited.
2. Closure of Industrial Units:Industries using unapproved fuels are shut down.
3. Vehicular Restrictions:Entry of trucks into Delhi is halted, except for essential goods.
4. Stop on Non-Essential Activities:Brick kilns, stone crushers, and hot mix plants are prohibited from operating.

Significance:

1. Stage IV is considered disruptive due to its impact on industries, transportation, and daily life. It emphasizes cooperation from the public and enforcement agencies.

What is AQI?

• AQI (Air Quality Index) is a numerical scale used to measure and communicate the quality of air in a specific area, indicating how polluted the air is and its potential health impacts.

Features of AQI

Parameters Measured:

1. Common pollutants included:
   1. Particulate Matter (PM10 and PM2.5)
   2. Nitrogen Dioxide (NO₂)
   3. Sulfur Dioxide (SO₂)
   4. Carbon Monoxide (CO)
   5. Ozone (O₃)
   6. Ammonia (NH₃)
   7. Lead (Pb)

AQI Categories and Health Impact:

The AQI scale is divided into six categories, each representing a different level of air pollution and associated health impacts:

AQI Value Range	Category	Health Impact
0–50	Good	Minimal impact
51–100	Satisfactory	Minor breathing discomfort for sensitive individuals
101–200	Moderate	Breathing discomfort for people with asthma or heart disease
201–300	Poor	Health impacts on sensitive groups; general discomfort
301–400	Very Poor	Increased risk of respiratory illness; severe discomfort
401–500	Severe	Affects even healthy individuals; serious health effects