National Air Quality Index (AQI): Understanding India's Air Standards

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Key takeaways

The Ministry of Environment, Forest and Climate Change (MoEFCC) launched India's National Air Quality Index (AQI) on September 17, 2014, under the Swachh Bharat Abhiyan.
The index is developed by the Central Pollution Control Board (CPCB) in technical collaboration with IIT Kanpur.
The official system tracks 8 criteria pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb.
India categorizes air quality into 6 colour-coded health bands, ranging from Good (0-50) to Severe (401-500).
India caps the official national AQI scale at 500, using the worst-pollutant principle to highlight the highest risk pollutant.

Delhi recorded an official AQI of 370 after Diwali firecracker emissions caused severe air pollution in many areas.
Private monitoring applications reported extreme pollution levels with readings close to 1,000 at several locations.

The National Air Quality Index (AQI) translates complex pollutant data into a single numerical score, colour code, and health risk category.

The Ministry of Environment, Forest and Climate Change (MoEFCC) launched the AQI on September 17, 2014, under the Swachh Bharat Abhiyan initiative.
The Central Pollution Control Board (CPCB) formulated the index with technical support from IIT Kanpur and environmental health experts.

India classifies air quality into six standardized colour-coded bands, starting with 0 - 50 as Good (Green) with minimal health impact.
The Satisfactory category (Light Green) covers 51 - 100 and causes minor breathing discomfort to sensitive individuals.
The Moderate category (Yellow) spans 101 - 200 and causes discomfort to people with heart, asthma, or lung diseases.
The Poor category (Orange) ranges from 201 - 300 and leads to breathing trouble for most people on prolonged exposure.
The Very Poor category (Red) spans 301 - 400 and can trigger respiratory illnesses after long exposure.
The Severe category (Dark Red / Maroon) covers 401 - 500, affecting healthy people and severely harming those with existing medical conditions.

The system monitors eight criteria pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb to determine ambient air quality.
The overall index relies on the worst-pollutant principle, which uses the highest sub-index value so high individual pollutant levels are not hidden by averaging.
Calculating the AQI requires data for at least three pollutants, which must include either PM2.5 or PM10.
India caps its official AQI scale at 500, even if actual pollutant concentrations go above severe limits.